J,' 253

Progress Report No. 2 1981 -1984

Arbeitsgruppe Strahlenschäden in Festkörpern

BERICHTE DES HAHN-MEITNER-INST1TUTS

Das HAHN-MEITNER-INSTITUT FÜR KERNFORSCHUNG BERLIN GMBH gibt eine Serie von Berichten heraus, in der Forschungs- und Entwicklungsergebnisse des Instituts mitgeteilt werden.

Die Berichte werden in der Referate-Zeitschrift „Informationen zur Kernforschung und Kerntechnik" der Zentralstelle für Atomkernenergie-Dokumentation (ZAED), in den „Nuclear Science Abstracts" der USAEC und im „INIS atomindex" ange­zeigt und referiert. Sie können von der Institutsbibliothek angefordert werden.

REPORTS OF THE HAHN-McITNER-INSTITUTE

The HAHN-MEITNER INSTITUTE FOR NUCLEAR RESEARCH BERLIN GMBH publishes a series of reports, in which research results are reported.

These reports are listed and abstracted in the Abstract Journal „Informationen zur Kernforschung und Kerntechnik" of the Zentralstelle für Atomkernenergie-Doku­mentation (ZAED) in the „Nuclear Science Abstracts" of the USAEC and in „INIS atomindex". The reports may be requested from the institute's library.

HAHN-MEITNER-INSTITUT FDR KERNFORSCHUNG BERLIN GMBH

I

•S"N

aw u/itärt^

V

Picture by M.C. Escher "Das Werk von M.C. Escher", picture number 212, Heinz Moos Verlag, printed by kind permission of the publisher

Progress Report No. 2 1981 -1984

Arbeitsgruppe C 2 Strahienschäden in Festkörpern

Hahn-Meitner-Institut Berlin GmbH Bereich Kernchemie und Reaktor Glienicker Straße 100 D-1000 Berlin 39

October 1984

u

Preface '^•~'\\J^te?t

This progress report no. 2 refers to the work performed for the R&D project 3.2

"Radiation Damage in Solids" of the Hahn-Meitner-Institut für Kernforschung,

Berlin in the period 1981 - 19841 Progress report no. 1 eonoomg the work Inf M - ^ "

CUtdt&OSh&ÜQ——l&81_£etrt- of prliit)i These gepesta aue(prepared on the occasion of the

review sessions of the committee of consultants (Wissenschaftlicher Beirat des

HMI). These sessions take place in fall every year. Each project of the Hahn-

Meitner-Institut is reviewed every four years. /

•Tho work reported would not have boon realized without the active and fruij

cooperation of the members of the group's tectmissLL-»t€tft'.'~Es8&ntial support was

also due to the HMljexsji€e-dlvts"Ions, Workshops and Electronics and Data Pro- H J^

L r r ^ " t h ° ^"c-" ^iu

ty(M. H. Wollenberger

(Leitender Wissenschaftler)

Abbreviations:

AP - Atom P r o b e DNS - Diffuse Kfeutron Sca t te r ing EDAX - Energy Dispersive Analysis of 3C-rays FIM - ^Field _Ion Microscopy RBS - Rutherford ISackscattering Spectrometry SANS - j t aa l l Angle Neutron p a t t e r i n g SIMS - j > e c o n d a r y Ion Mass S . P e c t r o s c o P y STEM - j>canning ^Transmission Electron tlicroscopy TEM - t ransmission Electron Mcroscopy

RESEARCH A C T I V I T I E S

OBLEMS T U D I E D

A P P L I E D M E T H O D S C°? S » ^ ^

^v*°v*v* ^ Vv 0 t V 6

^»«v , ^ 5 ^ ^ »<** X * <?• V * ^ • ^ R E S U L T S

stopping Powers, Ranges

Sputter Yields

Mixed Interstitial Configurations

Defect Reactions and Agglomerates

Atomic Diffusi

Atomic Redistribution

Phase Transformations

Microstructural Changes

O

O 4»

o U

n O o

O <•—O O

O » ^ • —

Systematica of electronic stopping power dependence on projectile target combination, range data for He, B and N in many solids TRIM code simulations for monoatomic and composite materials, layer structures

Structural classification of mixed interstitials in Mo and Al

Conditions for cavity production in self-ion and a irradiated ferritic steel (1-4914) and Fe12Cr

Diffusion coefficients in concentrated alloys and for various solutes in self-ion irradiated Cu, Ni and Fe20Ni2OCr. Identification of mixed interstitial migration for Be in Cu Characteristic; quantities of Ni surface segregation in CuNi by self-ion and a irradiation

Characteristic quantities of irradiation induced Se segregation in Cu. Kinetics and morphology of unmixing of CuNiPe alloys, influence of e" and n irradiation

Morphology of precipitates in Nimonic PE16

Approximate mean expenditure of professional manpower (including guests and thesis workers) .ii 1981 - 84 manyears/year

HAHN-MEITNER-INSTITUT Bereich Kernchemie und Reaktor

Arbeitsgruppe C 2 Strahlenschaden in Festkörpern

Leiter: H. Wollenberger

Contents

II. REPORTS.

Page

I. SUMMARY OF ACTIVITIES AND RESULTS 1 H. Wollenberger

1. ION-TARGET INTERACTIONS 8

1.1. Foundations in Ion Transport Theory 8 J. P Biersack

1.2. Applications of TRIM for Range and Damage Distributions, 17 Sputtering and Atomic Mixing of Solid Materials under Ion Bombardement J. P. Biersack

1.3. Experimental Verification of the Simplified Stopping Function 21 P. Mertens and Th. Krist

1.4. Z 2 -Oscillations in Electronic Stopping Processes of Protons 25 P. Mertens and Th. Krist

1.5. Target Thickness Dependence of the Electronic Stopping Power 28 P Mertens, A. Koch and Th. Krist

1.6. The Use of (n,a), (n,p) Reactions with Thermal Neutrons 32 and Rutherford Backscattering (RBS) for Depth Profile and Stopping Power Measurements

D. Fink, J. P. Biersack, K Tjan and M. Städele

2. DEFECT CONFIGURATION AND KINETIC STUDIES 35

2.1. Model for Self-Interstitial Trapping by Solutes 35 C. Abromeit

2.2. Effective Defect Production Rate for P1 ilsed Irradiation 38 V. Naundorfand C. Abromeit

2.3. Localization of Displaced Impurity Atoms in Irradiated 40 Aluminium Alloys from Channeling Experiments M. Müller

2.4. Lattice Location of Impurity Atoms Studied by X-ray 44 Excitation with Channeled Ions K.H. Ecker

2.5. The Lattice Positions of B in Si at High Implanted Doses 47 and Annealing Temperatures D. Fink, J. R Biersack and K. Tjan

3. THERMAL AND IRRADIATION ENHANCED DIFFUSION 48

3.1. Thermal Diffusion of Cobalt and Nickel in Copper 48 ft Döhl, M.-R Macht and V. Naundorf

3.2. Radiation Induced Diffusion of Be, Mn and Ni in Copper 51 H.-J. Gudladt, M.-R Macht and V Naundorf

3.3. Fast Interstitial-Solute Complex Diffusion under Irradiation in CuBe 54 H.-J. Gudladt, V. Naundorf and M.-R Macht

3.4. Diffusion in Austenitic FeCrNi and in Ni under Irradiation 56 A Müller, M.-R Macht, V. Naundorf andRV. Patil (BARC Bombay, India)

3.5. Short Range Ordering Kinetics in Electron Irradiated a-Brass 58 C. Abromeit andR. Poerschke

3.6. Dependence of Electrical Resistivity on the Degree of Short Range 61 Clustering in a NiCu Alloy W. Wagner and ft. Poerschke

3.7. Resistivity Studies of the Short Range Clustering and Long Range 63 Decomposition in Electron Irradiated NiCu Alloys S. Kophamel, ft. Poerschke and W. Wagner

3.8. Deviations from Matthießen's Rule in Electron Irradiated NiCu Alloys 65 B. Kophamel, ft. Poerschke and W. Wagner

3.9. Diffusion and Detrapping of Helium and Lithium Implanted in Metals 66 D. Fink. K. Tjan and J. P. Biersack

4. MORPHOLOGY AND KINETICS OF THERMALLY ACTIVATED ALLOY DECOMPOSITION _ 67

4.1. Analysis of Carbide Formation in Iron-Chromium Alloys by 67 Field Ion Microscopy ft. Lang

4.2. Atom Probe FIM Study on G. R Zone and7" Phase in an 68 Aged Cu-2.1 wt% Be Alloy F Zhu and P. Mertens

4.3. Thermal Decomposition in CuNiFe Alloys. Reld Ion Microscope and 71 Atom Probe Investigation W. Wagner, J. Piller and P. Mertens

4.4. Thermal Decomposition in CuNiFe Alloys. TEM Investigation 74 R.PWahiandd Stajer

4.5. Thermal Decomposition in CuNiFe Alloys. Neutron Diffraction Study 76 W. Wagner andR. Poerschke

5. MORPHOLOGY AND KINETICS OF ALLOY DECOMPOSITION UNDER IRRADIATION 79

5.1. The Influence of Cascade Effects on the Stability of Precipitates 79 C. Abromeit and V. Naundorf

5.2. Radiation Induced Instability and its Influence on the Decomposition 82 of a Concentrated Alloy C. Abromeit and K. Krishan (RRC Kalpakkam, India)

5.3. Radiation-Induced Segregation in NiCu Alloys 84 W. Wagner, V. Naundorf, L £ Renn * and H. Wiedersich" (' ANL Argonne, USA)

5.4. Short-Range Clustering and Long-Range Periodic Decomposition 87 of an Electron Irradiated NiCu Alloy W, Wagner and R. Poerschke

5.5. Electron Irradiation as a Tool for Alloy Decomposition 90 Studies at Low Temperatures: Neutron Scattering on Electron Irradiated NiCu Alloys R. Poerschke and D. Schwahn (KFA Jülich)

5.6. Neutron Scattering Studies of the Short Range Cluste. :> g and 92 the Long Range Decomposition in CuNiFe Alloys ft Poerschke, H. W. Golling and D. Schwahn (KFA Jülich)

5.7. Formation of Dislocation Loops in CuNi under 300 keV Cu + Ion Irradiation 95 R Dauben and ft P. Wahl

5.8. Morphology and Kinetics of Microstructural Evolution in a CuBe Alloy 96 under 300 keVCu+ Ion Irradiation ft. Koch and ft P. Wahi

5.9. Microstructural Evolution in a Cu-1.35 at.% Be Alloy under Electron 101 Irradiation in a High Voltage Microscope ft P. Wahi

5.10. Void Formation and Phase Stability under Heavy Ion Irradiation in 104 Ferritic and Austenitic Alloys P. Dauben, J. Tenbrink andR.R Wahi

6. HIGH TEMPERATURE FATIGUE OF SUPERALLOYS 106

6.1. Characterization of Precipitation Processes in Nimonic PE16 by TEM 106 and the Correlation to Mechanical Properties HP Degischer, H. Strecker and ft. P Wahi

7. EXPERIMENTAL DEVELOPMENT: IMPLEMENTATION OF A FIELD ION MICROSCOPE 109 P. Mertens, U. Vidic and H. Becker

III. PUBLICATIONS, DIPLOMA AND DR. THESES 115

IV. HMI-REPORTS, PATENT APPLICATIONS 126

V. LECTURES, UNIVERSITY LECTURES 127

VI. COOPERATIONS 147

VII. LEAVES TO FOREIGN INSTITUTES 149

VIII. GUEST RESEARCHERS 150

IX. STAFF 152

I. SUMMARY OF ACTIVITIES AND RESULTS H. Wollenberger

Activities and results of the group in the years 1981 - 1984 are sketched in the preceding graph on activities. Emphasis has been placed on studies in the key area of ion solid Interaction, irradiation induced atom transport and irra­diation Induced phase transformation* The applied methods of investigation gene­rally require facilities as being operated in large research centers rather than at university Institutes. This criterion does not necessarily refer to large scale hardware as for nuclear reactors or accelerators, but also to highly sophisticated software which requires long term and manpower consuming develop­ment as for diffusion coefficient determinations or field ion microscopy in irradiated samples. Selection of these methods has been guided by the goal of generating materials property data which are truly complementary in view of a sound understanding of the underlying mechanisms. Good examples are small angle neutron scattering and field ion microscopy applied to alloy unmixing.

The contribution to the European research programme on fusion reactor technology has to some degree been reoriented from more fundamental studies of defect pro­perties to "swelling and phase stability of steels up to high damage levels" according to requirements of the European Community (EC) Authorities.

A new and additional activity has been started in 1983 within a joint project on high temperature fatigue problems of superalloys. This project on "develop­ment of experimentally founded models allowing optimization of materials and components for high temperature application ander cyclic loading" is accomp­lished together with the Institut für Metallforschung, Technische Universität Berlin (TUB), and the Bundesanstalt für Materialprüfung, Berlin (BAM). Parallel studies are conducted on mechanical behaviour (TUB), microstructural evolution (RMI) and modelling of the mechanical behaviour by finite element calculations (BAM). The project is financially supported by the Stiftung Volkswagenwerk. Wi­thin the first year the microstructural work was dedicated to the precipitate morphology of the project standard alloy Nimonic PE 16 and the definition of re­ference alloy states for the forthcoming mechanical tests.

With the new project and an enhancement of the manpower expenditure for the EC fusion technology work, the number of coworkers increased by 6, all holding temporary positions. The number of "Doktoranden" increased to 8. The total num­ber of coworkers amounts to 40 (including one to two guest researchers on the average) by the end of 1984,

The basis of experimental facilities has considerably been broadened by imple­menting the field Ion microscope with atom probe, by moving the 350 kV heavy ion accelerator SIB from its earlier location at the Free University to the HMI and Implementing a complete new versatile beam guide system for five different lrra-

- I -

dlatlon positions, and by Installing a 2.5 MeV van-de-Graaff generator for p and a particle acceleration which replaces a 25 year-old 0.6 HV cascade generator.

The preceding graph on the research activities demonstrates to some degree the Interdependence of the different research tasks. The various scientific ques­tions are studied by applying more than Just one method of Investigation. Empha­sis Is put on combinations of true complementary methods. Two examples are des­cribed more below. By applying one and the same method to different questions, a better knowledge on the limitations of this method Is obtained. In addition, aspects which are relevant with respect to the chosen method are seen on a broader and more general base. Close lnterdependency Is further created by studying the different problems with the different methods on one and the same model alloy whenever It Is possible and this approach appears to be fruitful.

The study of electronic stopping powers of Ions In solids Is based not only on the three different methods of Investigation, It Is also an example for pur­posive cooperation with research groups abroad. As the electronic stopping power essentially determines the range of Ions in solids, there is a great practical Interest in their precise magnitudes for all kinds of Implantation work. Never­theless, reliable measurements have still been rare. Therefore a spectrometer of high resolution for the energy of ions having passed solid samples was built and stopping powers have been measured for a large number of target and projectile elements. For the determination of sample thickness by backscattering, the locally available maximua ion energy of 350 keV resulted in a comparatively large uncertainty of the thickness determination. By close cooperation with the group at the Queen's University, Kingston, Canada this problem could success­fully be solved.

In exploring stopping powers for all the elements of the periodic table proton projectiles play a crucial role because of scaling properties which allow quan­titative conclusions from proton stopping powers to those of other projectiles. In order to assure high precision particularly for such data joint measurements were performed with the group at the Johannes-Kepler-Unlversity, Linz, Austria which is specialised in proton backscattering measurements. Deviations of energy loss data as obtained from backscattered and transmitted protons are jointly studied because of the importance of this problem.

The spectroscopy of a and p particles from thermal neutron-induced nuclear reac­tions applied to implanted probe atoms yields particle ranges in solids and with this the stopping power depth integral. These measurements are performed at the ILL Grenoble by using a dedicated measuring position. The work is jointly per­formed with a number of external researchers who are often interested in parti­cular implantation profiles.

- 2 -

Theory Is not yet In the position to calculate stopping powers from first prin­ciples. By the use of fitting parameters and scaling procedures, however, quan­titative predictions for given projectile terget combinations are possible. The necessary comparison of theory and experiment is often done by means of the TRIM simulation code for ion solid interaction. Continuous Improvement of this code within many joint projects with groups all over the world contributes to a rapid and reliable data assessment for all ion implantation and sputtering work.

From the many different aspects of materials properties in radiation environ­ments, diffusion and phase transformations are being investigated. Knowledge of diffusion coefficients for defects and alloy constituents under irradiation is of particular importance when damage modelling is to predict reliably the micro-structural evolution of an alloy under given Irradiation conditions.

Phase transformations under irradiation are exciting phenomena by many reasons. The irreversible defect annihilation Introduces the main feature of irreversible thermodynamics* The existence of defect sources and sinks creates open systems, and the defect flux between sources and sinks drives these systems. With vanishing irradiation intensity the systems approach conditions of equilibrium thermodynamics. In the boundary range the atomic diffusivit/ may be enhanced considerably as compared to the non-irradiated case without introducing signifi­cant effects of irreversible thermodynamics. Understanding of phase transfor­mations under Irradiation is also of great importance for the development of structural materials for the forthcoming fusion reactor.

Besides diffusion and phase transformation the graph of activities lists three more topics under alloys and materials in radiation environments. Mixed inter-stitials in their plainest form are dumbbells consisting of one solute and one solvent atom. They are of great interest with respect to atomic diffusivity, because under favourable circumstances they cause extraordinary rapid solute transport. Such a phenomenon occurs for Be in Cu, for example (see also more below). Only by combined application of the common channeling technique and Monte-Carlo simulation of the channeling experiment, reliable conclusions can be drawn on the mixed dumbbell configuration under favourable conditions. This is the essential result of our work.

The defect reaction and agglomerate studies preferentially concerned the EC fusion technology task. Here, swelling behaviour and phase stability of the ferritlc steel 1.4914 and the base alloy Fel2Cr are studied for high fluence levels of self-Ions. The effect of He on these phenomena have been studied by preinjection of this element. A 30 keV He accelerator for simultaneous He injec­tion in self-ion irradiated samples (dual beam configuration) is being imple­mented Just now.

- 3 -

Atomic diffusion Is studied by three different methods and as the atomic redis­tribution studies yield information on the atomic diffusion as well, five methods are indeed applied. The profiling techniques resolve diffusion profiles more or less directly. Resistivity measurements are used to follow the kinetics of the atomic short range order evolution In concentrated alloys. By appropriate theories diffusion coefficients are then derived from the kinetics of the short range order evolution. Depth profiling by SIMS has particularly been developed for measurements in Irradiated samples and new fundamental insights in radiation induced diffusion mechanisms have already been obtained. This result is also due to the investigation of different questions and application of different methods to the same dilute CuBe alloy, the second question being :he kinetics of radia­tion induced Be segregation and the method TEM. As the results from the diffe­rent tasks are really complementary, this case is described here in more dec^il.

The study of the behaviour of Be in irradiated Cu goes back to the question of binding between structural point defects and solutes. Thermally activated dif­fusion in substitutional solid solutions is caused by vacancy migration. Diffu­sion coefficients of solute atoms in general differ from the, self-diffusion of the solvent. The difference arises largely from the binding between solute and vacancy. In the fact-centered cubic metals binding energies smaller than .3 eV have been determined.

In irradiated metals we have migrating interstitlals in addition to migrating vacancies. Rough estimates based upon elasticity theory show considerably larger binding energies for solute interstitial pairs than for solute vacancy pairs. The estimated relationship between binding energy and migration energy of such a bound pair suggested the possibility of an extremely fast solute transport. A high probability for the occurrence of this effect was found for undersized solutes. As the atomic volume of Be in Cu is about 30£ smaller than that of Cu, this system seemed to be well suited for respective studies. Earlier experimen­tal investigations indeed led by Indirect conclusions to an extremely fast Be transport.

The diffusion coefficient measurements in self-ion irradiated single crystals by means of dynamical SIMS measurements yielded a behaviour of Be which consider­ably deviated from that of other solutes in Cu. Main feature was a long range transport of Be out of the Irradiated zone into the pure Cu single crystal. At the same time the diffusional broadening of the original Be profile did not show any extremely large diffusion effect. The long range diffusion could not be explained by any other transport mechanism than by the Be interstitial pair migration. The experimental data directly yielded boundaries of the activation

- 4 -

energies for both binding and migration. Within the liradi.ited zone, the dif­fusion coefficient for Be at 300 K was found to be by one order of magnitude smaller than that concluded from the transport into the non-irradiated zone.

This discrepancy can be explained by an effect which is inherently connected with the complex migration. The interstitial tends to annihilate at sinks like dislocations and grain boundaries and thereby drops the Be solute close to the sink. More arriving pairs enrich the Be content near the sini until the solubi­lity limit is exceeded and precipitation occurs. Because of rhe strong coupling the solvent Is rapidly emptied of solutes and the diffusion coefficient would soon appear to be zero because of the lack of diffusing species. The non-zero one which was measured in the irradiated zone, must, according to our conclusion arise from a partial re-dlssolutlon of precipitated Be by the cascade mixing effect.

This interpretation of the measured diffusion coefficients in the irradiated zone called for demonstration of Be precipitation and re-dissolution by other methods. Transmission electron microscopy has been chosen in order to prove the existence of precipitated Be. Indeed precipitation of the Y-phase (50 at.? Be content, long-range ordered, body-centered cubic) was found after self-ion irra­diation of undersaturated 1.35 at-Z Be containing samples. By detailed measure­ments of tV.e growth kinetics of these precipitates a transition period and a steady state of the volume fraction of the precipitates was found.

The measured growth kinetics of the precipitates could be explained quantita­tively by the Be interstitial pair diffusion to the precipitation sites with the diffusion coefficient derived from the SIMS measurements and by precipitate dissolution as caused by cascade mixing. The entire Investigation gives for the first time quantitative Information on an interstitlally transported solute and the rate constants for its precipitation and precipitate dissolution.

Phase transformations are studied by three different experimental methods of microstructural analysis. FIM is complementary to TEM and SANS in an Ideal sense. Its application is extremely helpful for phase transformation studies in concentrated alloys. This has been demonstrated for the thermally activated unmixing of CuNiFe alloys with Ni contents of 46 and 48 at.I? and Fe contents 4 and 8 at.X, respectively. The SANS measurements demonstrated the high sensiti­vity of this method. A short range order (cluster) variation as produced by a mean rate of 0.1 jump per atom could indeed be detected. As the studies of ther­mally Induced unmixing in literature do not report on similar early stages, the studies had to be started with investigations of the unmixing kinetics of these alloys outside radiation environments *

- 5 -

The neutron diffraction measurements of states quenched from above the misclbl-lity gap Into it showed a periodic decomposition parallel to <100>, starting with wavelengths around 2 run. The coarsening of this structure upon thermal annealing was followed up to a wavelength around 10 nm. Although the kinetics of such a process can be studied in great detail by diffraction methods, the spa­tially varying alloy composition cannot be evaluated in a unique manner. This Is true also for the TEM and EDAX analysis as long as the characteristic decom­position length remains below 10 nm. TEM images show the typical Interference contrast arising from the periodic structure. From the distance of the satellite spots around the fundamental lattice reflections in the diffraction pattern, the wavelength of the structure was determined during further coarsening up to 20 nm. The detailed morphology of the two phases as well as their composition was ob­tained by FIH with AF from the wavelength of about 3 nm upwards. According to these results the alloy decomposes Into two phases, a Ni-rich which contains al­most the entire Fe ingot and a Cu-rich one. At the earliest stage resolved by FIH the phases form particles often interconnecting with the tendency to form chains along <100>. With proceeding coarsening they form a ramified structure of parallelepipeds being parallel to <100>. This structure eventually transforms to parallel plates with edge lengths amounting to about 5 times the thickness.

Though the morphology changes to some degree during the coarsening, the wave­length of the periodic structure was found to increase with time according to

0.22 the power law t for the whole range of coarsening (2 nm - 20 nm). Such a large range has not often been studied as yet, but obviously ought to be in or­der to prove reliably the validity of modern theories on phase transformation kinetics (cluster dynamics, e.g.).

The aost important result of the as>ik ii the initial »avei£u£?h sf 2 a which does not depend on the annealing temperature. From this result and the knowledge of the short range clustered state of the alloy at the quenching temperature above the mlscibllity gap we conclude the embryo clusters from which the coar­sening evolves to be those already existing In the quenched state. It Is obvious that the classical descriptions of nucleatlon and growth and splnodal decomposi­tion are not really suitable for this kind of unmixing.

Based upon the detailed knowledge of kinetics and morphology of the thermally Induced CuWiFe unmixing, the Irradiation influence can now reliably be studied. Preliminary Investigations have shown the expected diffusion enhancement, but also new features of the unmixing kinetics. The obtained results demonstrate the usefulness of the combined application of SANS, TEM and FIM with AF. Although the CuNlFe system seems to be kind of a model system with respect to the appli­cability of all these methods of investigation, our preliminary results on N1A1T1 and Nimonic PE 16 are similarly convincing.

- 6 -

The joint project on high temperature faiigue ot aupesrai-iuys con-:si.s uf two more tasks which are not given in the graph on the research activities because they are performed in the cooperating external Institutions. The mechanical lou cycle fatigue and creep experiments, the samples of which are analysed here, will be performed in the Institut für Metallforschung der Technischen Universität Berlin. Data evaluation of mechanical experiments with respect to generalized materials property descriptions and finite element calculations aiming at the transfer of the sample results to structural components are performed in the BAH. Hence, the joint project in total applies quite different methods and aims at a comprehensive quantitative description of the phenomenon.

Last but not least the group provides experimental facilities and know-how for many researchers from other sections of the HMI and from other institutions. Out of the facilities, the 2.5 MeV e~ irradiation system and the neutron dif-fractometer T2 of the BER II are often provided for guests. Facilities for radioactive tracer work are provided continuously for one coworker of the Insti­tut fß- Metallforschung der Technischen Universität Berlin. Sample preparation and characterization Is performed for external researchers, particularly for difficult cases as zirconium-base alloys and lntermetalllc compounds.

- 7 -

1. ION-TARGET INTERACTIONS

1.1. Foundations in Ion Transport Theory J. P. Biersack

Introduction

Over the past four years, the foundations for the slowing down and scattering of energetic Ions (and recoil atoms) in solids have been completely revised. In practically all cases, i.e. with interatomic potentials, scattering cross-sec­tions, nuclear and electronic stopping powers, and the treatment of transport equations for obtaining projected range distributions, we found the traditional assumptions, approximations and methods inadequate to describe modern precision measurements. (The number of experimental data in this field Is rapidly increas­ing; by 1980 there were already over 600 publications per year, and more than 1200 ion accelerators installed in academla and industry).

The renewal of all the basic inputs and methods in transport theory was a huge task and could only be accomplished by close collaboration with my colleagues at the HMI and particularly with J.F. Ziegler, IBM Yorktown Heights, and U. Litt-mark, KFA Jülich. Some results on stopping powers and ranges have partly been published in a textbook /l/, and a more elaborate book /2/ will follow this year. - The now achieved precision corresponds to a standard deviation of better than 10X for low energy ions, and better than 3% for high velocity ions. Projec­ted range predictions have about the same accuracy.

Interatomic Potentials

About 650 pair potentials have been calculated from Hartree-Fock-Slater solid state atomic wave functions. Within the overlap volume the Coulomb and kinetic energies of the electrons, as well as exchange and correlation energies were determined in the sense of a first or respectively second order perturbation theory. The results were checked against 3elf-consistent-field molecular calcu­lations, fig. 1, as well as against experimental potentials, e.g., fig. 2, with satisfactory results.

In order to obtain an applicable result, we have made an attempt to fit all Individual screening functions of the potentials into a single, "universal" function. This was indeed possible by firstly varying the screening length a u

until th' variance of the individual screening functions reached a minimum; this resulted in

0.8853 a 0 au , (1)

Z l0.23 + Z 20.23 - 8 -

and the configuration shown In fig. 3. Secondly, this group of tightly bunched functions was least-square fitted to a "universal screening function" (Möllere type)

* u(x) - I Aie" B l* (2) 1-1

which yielded Aj. - 0.1818, 0.5099, 0.2802, 0.02817, Bt - -3.2, -0.9423, -0.4029, -0.2016.

Fcr a final check on this "universal" potential, the sunned square error (variance) was determined with 106 presently available experimental data on binary interaction potentials, see Table I, which clearly shows the improvement with respect to previously used popular potentials.

Table 1: Comparison of theoretically and experimentally determined potentials

Screening Screening Variance in Function Length comparison with

exper. data Moliere ajpp 237 Lenz Jensen »TFF 1 4^ Kr-C a„ 7.1 Universal a„ 4.8

Formalism for fast evaluation of scattering angles

Once the repulsive potential is known for an atomic collision, it is usually 2 necessary to determine the scattering angle 9 or the quantity sin (0/2) which is

proportional to the energy transferred to the target atom. This would normally require the solution of a difficult integral which we could replace by an analy­tical treatment with an average accuracy of 2% taken over the energy range be­tween e • 10~" and e » 10, see fig. 4, and built-in correct asymptotic behaviour for E + 0 (hard-sphere collisions) and e » 1 (Rutherford scattering). This so-called "magic formula" Is particularly computer efficient and saves valuable CPU time in determining cross-sections for the use in semi-analytic ion transport codes, or for direct applications In realistic simulations of ion scattering and slowing down (Monte-Carlo codes). Both applications have their individual merits and are of equal importance 72/.

Scattering Cross-Sections

Many theoreticians still apply the traditional concept of using cross-sections as a function of t^'2 » e'sin(9/2), which Is convenient and particularly at e-values above 10~2 a good approximation. For these applications we have derived a new analytic fit (1Z average error) as shown in fig. 5 for the universal poten­tial.

Although this fit yields accurate nuclear stopping powers, the concept of contracting the two variables e and sin(0/2) into one, t1/2, leads to gross errors In the different cross-sections at low energies, e.g., for e - 10~3, as depicted in fig. 6. In these cases, e < 10"2, we would strongly recommend to replace the cross-section a(t*/2) by the more suitable fit for o(e, sin 9/2) which is also shown in fig. 6 in comparison with the precisely determined cross-section.

Nuclear Stopping Power

The precise evaluation of the nuclear stopping power for the new universal potential yields the data points depicted in fig. 7. (The same values within about 1Z could also be obtained from any above mentioned scattering formula or cross-section). The solid line in fig. 7,

c 1/2 ln(l + 1.1383 e) B n {•>)

E + .01321 e-21226 + .19593 e -5

represents our analytic expression for the new nuclear stopping power. The stop­ping powers for other popular potentials have also been determined precisely and are shown In fig. 7 for comparison. As expected from the potential curves, fig. 3, the new stopping power is located between tue one for the Lenz-Jensen and the Möllere potential for e » 10"5 ...1.

Projected range distributions

Modern range measurements, e.g. /3/, yield information on several (up to four) moments of the range distribution, whereas traditional methods of theoretical range predictions were unable to scope with this situation. Fig. 8a indicates the typical discrepancies of the latest predictions (tables of Gibbons et al. 1975, and Brlce 1975) on just the first moment of heavy ion ranges in comparison

- 10 -

with modern data. If potentials, cross-sections, and stopping powers are im­proved according to the previous sections, the mean range can be correctly determined, fig. 8a, but the range straggling (second moment) is still poorly predicted, see the curve LZ (Littmark-Ziegler) in fig. 8b. The calculation of higher moments would be of even less realistic value. In order to improve on these difficulties, three new approaches in range theory were suggested:

The first approach /4/ consisted of setting up a system of differential equa­tions which could be solved efficiently on any computer, see curves labelled B in fig. 8, which was so far satisfactorily tested with the first two moments (mean range, longitudinal and lateral stragglings). These new equations turned out to even allow analytical solutions, see dash-dot lines in fig. 8b and fig. 9.

The second method consists of transforming the transport equation into a Vol-terra Integral equation, which can be solved numerically and even allows to exactly account for free surfaces. First results Indicate that now all projected range moments up to the 4th order can be predicted satisfactorily. As a further improvement over previous methods, both new approaches (differential or integral equations) allow for exact treatment of multi-element (composite) targets.

Our third approach on evaluating range and damage distributions consists of rea­listically simulating the individual events in scattering and slowing down of ions (and recoil atoms) by a Monte-Carlo computer program TRIM /5/. This program is now widely used and has been extended to treat all kinds of atomic collision processes in complex target structures, including such applications as defect production, sputtering, atomic mixing, etc., which will be described in a separate chapter.

Particle reflection and transmission

Besides of the mentioned realistic simulation in Monte-Carlo programs, light particle reflection (number, energy and angular distribution of backscattered ions) and transmission (angular and energy distributions of ions behind a foil) could be analytically treated with good precision /6,7/. Particularly the reflection of light Ions from fusion first walls, limiters, etc. Is of actual interest, and the new results, Indicating a much shallower drop-off with In­creasing energy than previously assumed, may find some Immediate application in connection with the upgrading of neutral beam Injectors to higher energies.

- 11 -

I\l J.P. Biersack and J.F. Zlegler, 2 chapters In "Ion Implantation Techniques"

(eds. H. Ryssel and H. Glawischnig), Springer Verlag, Berlin, 1982

HI J.F. Ziegler, J.P. Biersack and U. Llttmark, Vol. 1 of "Stopping and Ranges

of Ions in Matter", Pergamon Press, N.Y., 1984, In print

131 F. Jahnel, H. Ryssel, G. Prinke, K. Hoffmann, K. Müller, J.P. Biersack,

R. Henkelmann, Nucl. Instr. Meth. 182/183 (1981) 223

/4/ J.P. Biersack, Nucl. Instr. Meth. 182/183 (1981) 199, and Z. Physik A 305

(1982) 95

151 J.P. Blersack and L.G. Haggmark, Nucl. Instr. Meth. J^M (1980) 257 and

J.P. Biersack and W. Eckstein, Appl. Phys. A34_ (1984) 73

16/ W. Eckstein and J.P. Biersack, Z. Physik A 3_10 (1983) 1

PI M.M. Jakas and J.P. Biersack, Z. Physik A 3_1£ (1984) 29 and

T. Krist, P. Mertens and J.P. Biersack, Nucl. Instr. Meth. B2 (1984) 177.

9 O.I,

0.01 -

~ I — I — I — I — I — I — I — r

„L-L.

V "V

T 1 1 1 1 1—

^SCFab INITIO o FEG SOLID STATE oFEG FREE ATOMS

^ AI-AI

^=. ^

-1 1 I I I ' i i i i i i 2 4 6 8 10 12 |4 IS

REDUCED RADIUS X = r/o

Fig. 1. Interatomic screening functions based on various theoretical approaches:

self-consistent-field (SCF), our present free-electron-gas calculations from

HFS, solid-state charge distributions (FEG solid state), ar.d from isolated atom

charge distributions (FEG free atoms). The solid line represents our new univer­

sal potential.

Fig. 2. The scattering of energetic noble gas atoms from nobel gas targets give

information about interatomic potentialsV(r). The hatched area Indicates the

regime covered by experimental data. Present and previous theoretical predic­

tions are shown for comparison. In this case of closed electron shells the

theory Is seen to yield good results even below 1 eV.

- 12 -

In tera tomic Screening Potentials c - j 1 , . ( J

o ^ •2 i V a t t = .685« * .528 / ( Z ,°» + Z 2 °» ) o ^L e l 3 - : ^ ^ - .

\ ^ ^ . " ' * • * » • , • »

M S a "c 1 'V^S»^. ~~ "" """'—' ^

V"^N%.. s- - '"''- ^^^lifc^ o c/o \ ^ i ^ k ^ o \ , ^ \ r^^^s^

10 20 Reduced Radius ( r / a u )

Fig. 3. Plot of our individual screening functions using the new screening length a„ in comparison with some classical screening functions. The grouping of the individual curves is quite tight, with a standard deviation of 18Z.

iäüngir Formula For UNIVERSAL Potential

0 10 20 30 40

Dimensionless Impact Parameter (p/a)

Fig. 4. Simplified analytic description of the scattering angle 0 by the "magic formula" for the "universal" potential in the energy range c - 10~5...l (solid lines). The set of points are the exact solutions of the cosplete orbit equa­tion.

- 13 -

22S?Z£rm*m UNIVERSAL Potential

/ Spline Parameters

,"'m = I-exp(-«p£ai(0.1 In c/tj)') \ X, - 124.6 •, - 10-" \

», - -2.432 -O.IiOP 2.64b -Z.i*± I.2IS -D.166S "^

JO-» 10-» to" io-' i io' io' io' SQUARE ROOT of t

Fig. 5. Scattering formula of Lindhard, Nielsen and Scharff with only the single

variable t « E sin Q/2. The function fft 1/ 2) is evaluated using the universal

screening function (set of points) and spline fitted.

«>[M

1)00

30

—i i i m i | 1— i—rniii| '

£'10

./"

Jo" 10' -3 10' -2 10" .«•f

F g. 6. Comparison of different approximations to the different scattering cross

sections for the Möllere potential at low energy (e - 10~3) with the exact solu­

tion by the scattering integral: LNS approximations by Winterbon (H) and Litt-

mark-Zlegler (LZ), small angle approximation by Müller (M) and new analytic

approximation by Blersack/Kriiger (BK).

- 14 -

UNIVERSAL Reduced Nuclear Stopping T T ] 1 PTT] 1 TTT]—1 TTT—I I M|—I—TTT|—I—TTT] T

UNIVERSAL Scr«*nlng Podntiol #„ - D - U I ? * . - 1 1 * 4 ' • O . J M M . - * * « 1 ' " *o.ai02a.-* - w ' •o.o2»^71•-"• ,"•

1U IV IV l IV . '

Reduced Energy (c)

Fig. 7. Reduced nuclear stopping function Sn(e) for the "universal" potantial and some classical potentials. Points are exact calculations, solid line is the analytical function, eq. (3).

10' 10* ION ENERGY UtV]

Fig. 8. Heavy ion range* in silicon: (a) mean projected range compared to pre­sent and previous theories (Gibbon* et al., 2nd ed., and Brice tables), (b) also contains range straggling of recent preciaion measurement« in comparison vith results of classical (Littmark, Ziegler) and nev (Bieraack) range theories using the same potentials and stopping powers. Dash-dot line is analytic solution of new theory. Circles are own measurements, numbers indicate previous data.

- 15 -

L " u i i i — i " i . 11 i i — r

10° • I - . . . i I

102

ElkeV)

_ 10'

Fig- 9- Projected ranges of various light and medium heavy ions in Si: experi­mental data and new (analytical) universal range predictions based on present (ZBL) electronic stopping (solid line).

- 16 -

1.2. Applications of TRIM for Range and Damage Distributions, Sputtering and Atomic Mixing of Solid Materials under Ion Bombardement J. P Biersack

Computer simulation of the motion of Ions and recoils in solids has become a field of growing Interest over the last years. This has rialnly two reasons: (1) Ion Implantation and recoil Implantation Into Increasingly complex target struc­tures (multi-element, multi-layer), as well as various applications of sput­tering, have become Important tools In manufacturing semiconductor devices and also In.producing metal surface layers which could not be obtained by other means; (2) traditional analytic theories, such as the LSS theory, have severe difficulties in dealing with composed materials (e.g. tungsten carbide), with free surfaces or Interfaces, and even in establishing realistic cross-sections for low energy collisions.

A Monte Carlo computer program (TRIM) has been developed which simulates slowing down and scattering of ions and recoil atoms in amorphous targets in a realistic way. It was originally designed for determining ion range and damage distribu­tions as well as angular and energy distributions of sputtered, backscattered and transmitted particles with high precision. The computer program has then been extended to Include multi-element and multi-layer targets, which not only makes It useful for modern technical applications but also Is more rewarding in a scientific way, since very little Information on the behaviour of such systems under Ion Irradiation has been obtained previously. Among the new and Important effects in composite materials, e.g. is the depletion of the lighter component In the surface region by preferential sputtering and even more efficiently by preferential recoil implantation which then in turn leads to an enhancement of the light element at some deeper depth.

The Monte Carlo method as applied in simulation techniques has a number of dis­tinct advantages over present analytical formulations based on transport theory. It allows more rigorous treatment of elastic scattering, explicit consideration of surfaces and Interfaces, and easy Inclusion of multi-atomic targets. The major limitation of this method is that it is inherently a computer-time con­suming procedure. Even with modern computers there is often a conflict between available computer time and desired statistical precision. In the present Monte-Carlo program TRIM, we attempt to alleviate this problem by using analytical techniques wherever possible with good precision in order to reduce computer usage by at least an order of magnitude and at the same time sacrifice little accuracy in comparison with earlier Monte Carlo codes. This Is achieved mainly by applying an analytic formula for determining nuclear scattering angles, and by suitably expanding the average distance between collisions at high energies.

Some TRIM results will be shown in comparison with precise experimental data in the following figures. The examples chosen Include ceramic flrstwall-coatings of fusion devices, various metals and last but not least semiconductor applications.

- 17 -

KT" r

10*

j <He-Ti B2

r r - n - i — i :

! / / ; f /

l_i i, J i_i i ' •• • i i i in. i . i i i

S k t f H » ' — TIB, DEPTH OF. ORIGIN OF SPUTT. ATOMS

10 50 -oo 1000eV E J 1 l l . L j , ._ ]

^ 0 5 u s 20 25 30T

Fig. 1. (a) Total and partial sputtering yields of T1B2 under helium bombard­ment, (open symbols: TRIM, filled symbols: experiment), (b) the depth of origin of sputtered atoms.

.001

300 keV 3 He-Fe * VIRGIN I T R ) M

— CONVOL.J • EXP

10

.2 .4 .6 .8 .9 .10 Depth I /jml — -

.01

.001

300 keV 6Li - V I t VIRGIN 1 T R | M

— CONVOL./ • EXP

Depth l/im)

Fig. 2. Range distributions of light ions in metals as predicted and convoluted with the detector resolution in comparison with experimental data.

- 18 -

209 B i83 I o n s ( i20keV) into Si l icon Target

Eo

4

a

*7 "Q T Universbl ' Ion Distribution £JDLI stopping

• O'CONNOR.

1»1TR!M

0 200 400 600 100 1000 Depth into Target (Angstroms)

B »

5

O 0»

» •

r^ TRIM

A EXR DATA

BLLCrowdar

JQKtrach. Soc

46 0968)455

120 MV 0-175 J Sb+-~Si r-036

?fe 4Öö 5ÖS 555 555 Soc DEPTH (4)

Fig. 3. Range dlscrlbutlons of heavy Ions, Bl ind Sb, In silicon. Histograms are

TRIM, data points experimental results.

- 19 -

n B 5 Ions (200keV) i n t o W f i lm on SiO,

LOL Stoppinf "—'*• - — ——

2000 4000 6000 Depth into Target (Angstroms)

tiM. „ , * * * • * » »••*••• ' •

Particle Distribution Vacancy Production

Particle Distribution Vacancy Production Lateral Distribution from a Mask Edgi

>*• * M U M - " I , ^ *•• WW 11— Hill • I t

Particle Distribution Vacancy Production

Fig. 4. Boron implantation into a 2000 A W film on S102: TRIM results on longi­tudinal and lateral distributions of the implant and the vacancies.

- 20 -

Experimental Verification of the Simplified Stopping Function P. Mertens and Th. Krist

Introduction

Precision and variety of potential applications have made ion beam techniques a favoured method in analyzing and modifying materials. Thus an increasing need for stopping power data of ions in the low energy region (some hundred keV) de-veloped. These data may be provided by experiments, theory and scaling laws. In a situation where theoretical approaches are not of satisfying precision and experimental data are often inaccessible, -these scaling laws demonstrated in several compilations their importance for practical purposes /1-3/.

The scaling of electronic stopping cross sections is based on the factorization Se(Zi, Z 2, v) • P(Zi, v) • T(Z 2, v), where Z\ and Z 2 denote the nuclear charges of projectile and target and v is the projectile velocity /3/. This separation of Se(Zi, Z 2, v) into factors which merely depend on projectile or target is not justified by theory. Thus the limits of its validity have to be determined by experiments. In preceding measurements we found that the stopping ratios Q p = P^Zi, v)/P(2Zi, v) and Q T * T( 1Z 2 > v)/T( 2Z 2, v) are independent of Z\ and Z 2

within a limit of typically ± 102 [4]. Accordingly this uncertainty will be implied if the ßlmpllfied stopping function is used to scale from SeC^Z^, 1 Z 2 , v) to S e( 2Z- t > lz 2, v) or Se(*Zj_, 2 Z 2 , v). Furthermore the precision of a scaled crc3S section is given by the precision of Se(lZ]_, lz 2, v) and of the stopping ratio. The stopping cross section being an oscillatory function of Z^ and Z 2 it cannot be excluded that the stopping ratios undergo similar fluctuations, too. As a consequence stopping ratios derived for neighbouring elements in the perio­dic table or elements located in the minimum of the Z2-oscillations of S e might not be appropriate for elements of substantially different nuclear charge or elements in the regime of a maximum in the Z2-oscillations. Most of the stopping ratios published so far have been measured for light substances /5-7/. The ex­periments reported here include rare earth and heavy metal elements, to examine if stopping ratios valid for the light elements also apply to larger Z2-values, additionally the stopping ratios to scale S e from one ion to another are derived.

Experimental

Experiments were performed with 30-330 keV ions in the range 1 < Z\ < 5 for four groups of solid materials with 6 < Z 2 < 83 (see table 1). The target foils were produced by vacuum deposition and floating off in distilled water. Highly reac­tive materials like rare earth elements were directly evaporated in the target chamber on carbon foils. No absolute thickness calibration was needed for the determination of the stopping ratios. In order to additionally derive stopping cross sections for heavy Ions from our measured energy losses we used the cross sections for He as given in Zlegler's tables.

- 21 -

In the course of these measurements more than 30-000 data had to be collected. This multitude of data was absolutely indispensable for producing results of high reliability.

Results

As an example for the data accumulated the experimental stopping cross sections for the ions with 1 < Z\ < 5 in six selected materials are depicted in fig. 1. The accuracy of the stopping cross sections is mainly given by the quality of the foil thickness calibration, i.e. by the quality of Ziegler's fits for He +. It becomes apparent from the measured values that the function Se(Zi, Z2, v) is very similar for the different absorbers. So this plot is already visually sug­gesting the application of the scaling procedure among different materials. The stopping ratios for He +, Li +, Be + and B + related to protons are depicted in fig. 2. For the neighbouring metal elements the stopping ratios for all ions only differ by t 5X, i.e. a common stopping ratio would allot* to scale from one element to another within this error. The stopping ratios for carbon differ from the metal elements by about 10% for the lower energies, approaching those values at higher energies, however. In an earlier paper /6/ we have demonstrated that our stopp.» ~g cross sections for He + and Li + in C, AX, Cu, Ag and Au could be well scaled applying the Andersen-Ziegler cross sections for protons and Ziegler's stopping ratios. Most of the data Ziegler could base his fit on having been accumulated just for those elements, it had to be expected that his genera­lized stopping ratio could be first of all applicable to this group of ele­ments. In contrast to our former measurements the stopping cross sections for the elements in figs. 1 and 2 are not all located near minima in the Z2~oscil-lations of S e, but they also cover the transition from a maximum to a minimum of these oscillations. Therefore the application of Ziegler's master stopping ratios for scaling the cross sections of these elements constitutes a more cru­cial check of the validity of the simplified stopping function. In ref. /4/ it was shown that for the group of elements in figs- 1 and 2 the deviations between experimental cross sections and the ones scaled on the basis of the master ratios are much more severe than for C, Al, Cu, Ag and Au. In order to Investi­gate if this disagreement is mainly due to the restricted number of elements the master stopping ratios have been derived from, or if it is due to the limited validity of the simplified stopping function, we derived for our data set speci­fic stopping ratios and applied them for scaling on the basis of our stopping cross sections for He + (fig. 3). From the plot It becomes evident that almost perfect agreement between experimental and scaled values for this consistent data set has been achieved. It thus can be concluded that for this group of elements the simplified stopping function Is capable of scaling S e within an error of ± h%.

- 22 -

Our original Intention having been to check the validity of the simplified stop­ping function for a large spectrum of elements and to derive one set of stopping ratios Qp(Zi, v) and Qx(Z2, v) for scaling applications, we compared the stop­ping ratios obtained for four individual groups of elements (A: noble metals, B: transition metals, C: rare earth elements, D: heavy metals). Between group A and B the stopping ratios differ by less than ± 4Z. Related to group A the stop­ping ratios for group D are typically smaller by 5Z, while the rare earth ele­ment's group C exhibits stopping ratios smaller by 10 - 15Z. Therefore a unified stopping ratio applicable for scaling among any two elements of the periodic system will yield larger deviations (typically ± 10%). Excluding the rare earth elements results in stopping ratios valid for all the remaining materials Investigated within ± 6Z. Precise He+-stopping cross sections being available the stopping cross sections of these elements can be approximated within this error.

It thus is to be concluded, that the simplified stopping function has proven to be an universal and precise tool to approximate electronic stopping cross sec­tions. In spite of a slight influence by the Z2-oscillations of S e the stopping ratios can be applied as material-independent factors.

Ill W. Whaling, Handbuch der Physik, J34 (Springer, Berlin, 1958) 193 111 L.C. Northcliffe and R.F. Schilling, Nucl. Data Sect. AJ_ (1970) 233 /3/ J.F. Ziegler, The stopping and ranges of ions in matter, 2-6 (Pergamon

Press, New York, 1977) IUI P. Mertens and Th. Krlst, J. Appl. Phys. 22. (1982) 7343 151 P. Mertens, Phys. Rev. A 19 (1979) 1442 161 P. Mertens and Th. Krist, Nucl. Instr. and Meth. J 98 (1980) 33 HI S. Kreus8ler, C. Varelas and R Slzmann, Phys. Rev. B 16^ (1982) 6099

- 23 -

'Li*

" i tog

He* „»»» , .

Jß*L.

Be* «** _"»•

I T » » • • *

» » » - p n> m Mp. •> » » . M . m

"B-

< * : • :

« * - : :

.!•• £ lWtf|

a . so . y . w no. ijo

MepfHA9 MMdt« -

•> fUCkll • line

aMppiftg c-f«i* *«tliort«

H\ H«\ 'Li*. Be*, nB*

c o o . •- S Q. S.IBI Ol SeIH)

•s X 5 c o Ol

U ) * S.IB«)

o: 3 o z E O 2

8 * "

5%

, » S %

I- 5%

• : C • - V

* > C r • • Fe

v i Ni

« • Zn

S.IH)

10 20 30 tO SO 60 70 80

H j . II Total atopplaf. croa« «actio» for 30-330 kav

tooa alth 1 < I, < 5 lr. C, V, Cr, Fa. Hl and Zn.

rig. 21 Stopping ratloa Q» ralatlvo to hydrogoo for

Ha», 'U+, «.» ,„d Hl».

•3 « 30 35 X 35 iOlaV- 3« 39 » K lÄlaY

AajUcaltwi at lha aia 'aa* ' •'••»»•a laliaa Ha*'

• l i ­la*

• •aaapi aag JBBB- T W » y aiaaaaaaaanaj IBaPV*

Ht'l I .:»U* • : ! • * *;"•* '4.1* 1 * U t*«B I p,^„,!, . , t»".,ii*p« „o, • » * ( » * ••V'MMhl H f . | l M ^ H , s v t r s g t ( 1

Fl(. 3i Application of tha »tapping ratloa avaraiad

far our tari»t «lttMnta to acala fro« our

hclluB data to tha baavlcr looa.

1.4. Zg-Oscillations in Electronic Stopping Processes of Protons P Mertens and Th. Krist

The fundamental process of slowing down an energetic proton In a solid hus two closely related Important aspects: (1) behaving in the 10 keV region almost like an Ideal point charge the proton Is suited more than any other luu to probe the aolid's specific response to this moving charge, and (2) the stopping process for heavier ions can be scaled to the stopping of protons on the basis of an ef­fective charge conception. The measurements performed here contribute to both these aspects«

The electronic stopping cross section Se(Z^, Z2, v) at a fixed ion velocity v is an oscillating function of the nuclear ion charge Z; and of the target charge Z2' These Z^- and Z2-oscillations reflect the electronic shell structure of projectile and target. By experiments with protons in materials with 23 < Z2 < 30 we found /l/, that for the different materials the maximum stopping cross sections Se

ll>ax occured at different energies E(S em a I C). But as only data for a

small number of materials were available, it could not be decided whether ECSe"18*) was related to Z2 In any systematic way. Therefore these experiments have been extended to 23 elements In Che range 6 < Z2 < 83.

The physical foundations of ECSe™8*) still being unclear, it is nevertheless helpful to predict E(S e

m a x) for materials, where only scarce experimental data exist. For example, juat In the region of the stopping maximum the sophisticated fits for S e by Andersen-Zlegler 111 are the results of interpolating the low energy regime and the high energy regime uaing an algorithm proposed by Varelas and Biersack /3/. Knowing where to locate E(S e

D a x) could contribute to the pre­cision of those fits. By means of verifying a principle of correspondence be­tween a maximum for Sg111835 and a minimum for ECSg"18*) and vice versa our experi-menca are of considerable help in constructing the functions Se(l, Z2, v).

In fig. 1 all our experimental results for Sa 0 3* and E ( S em a x ) are comprised.

This consistent and relatively comprehensive data set reveals that E(S em a , t) is

subjected to Z2-oscillations as is Sg™3*. While the periodicity is identical for Se"ax and ECSg1118*), the amplitude is inverted. For the lighter elements the amplitude of the E(Se

max)-oscillations seems to be higher than the amplitude of the Se

max-oscillation8. S em a x and E(S e

m a x) as resulting from the Andersen-Zlegler fit are shown in the figure as continuous and dashed line. The bar at the top of this diagram la Indicating, if the fit for the specific element is based on any experimental data. In the high Z2~range covered by the measurements experlmencal daca were only presenc for Ta, Au, Pb and Bi. Nevertheless, the agreement for E(S e

m a x) between experiment and fit is almost perfect, pointing to a realistic approach of the Varelas-Biersack algorithm for interpolating the low energy and the high energy stopping cross sections. On the other hand, our ex­periments obviously define E(Semax) with high precision.

- 25 -

In the scope of these measurement» a lov stopping cross section S em a x appears to

be strictly correlated to a high energy E ( S eB a x ) . The Andersen-Zlegler fit does

not reproduce this behaviour In the region with 23 < Z2 < .10. Irrespective of almost identical values for S a

a , x the positive osciU.ion of 2(3^*) Is shif­ted for the flta to the lower Z2~range by approximately two units. Examining the underlying experimental data, It becomes apparent that the fits were confronted with a distinct ambiguity between certain low energy and high energy data. An application of the principle of correspondence of a low S e"* x and a high E ( S e

a a x ) , found here, would have contributed to consistency and precision of these fits.

Finally It Is to be concluded that for protons the energy at maximum stopping croas section E(S e"* x) Is even more sensitive to the target's electronic struc­ture than Is S €

M * . The measurements presented here can serve as a consistent data base appropriate to detail our understanding of the stopping process.

/I/ P. Hertens and Th. Krlst, Nucl. Instr. Meth. U>4 (1982) 57 111 H.H. Andersen and J.P. Zlegler, Hydrogen stopping powers and ranges In all

elements, Pergamon, Hew York, 1977 /3/ C. Varelas and J.P. Blersack; Nucl. Inatr. Meth. 79 (1970) 213

- 26 -

•s i targe* materials with fits based en experimental vaiues C 3 target materials with fits based on interpolation

-30

'h

i « tjK w nit -a ana

Proton stopping power 50

40 u • /I I I I I I I I I

!i • i 1 1

i\ M l » I I I I / Y'

, * *

i ! i l ' i

/ IN • /

»"»J i

• • i i n

I V • I'll

\t r — s-.

E (Se™,)

0 *S 10 15 20 25 30 35 40 45 SO 55 60 65 70 75 80 85

M 170-M •

* ' r 160-

J A -/ '

150-

\ / '• '' i A / w w 140-\ / '• '' i A / w w

I 130-

° A > \

ÜJ 110-

100-

from Ziegler 90-

from Zi«gler 80-

this work 70-

this work 60-

z2 so-•L X

Fig. 1: Z2-osclll«tlon of the nnxlmim stopping cross section S^ 9 1 3* and the proton energy at S e

m a x .

- 27 -

1.5. Target Thickness Dependence of the Electronic Stopping Power R Mertens, A. Koch and Th Krist

Ion beam techniques for Modifying the characteristics of a material and for analyzing materials require an accurate knowledge of the stopping process of energetic particles in solids. But In spite of the growing need for stopping data even fundamental information is missing. Until now there has been a con­troversy about the question if the energy loss &E of energetic ions is a li­near function of th* distance d travelled through a thin target foil. To inve­stigate the function 4E(d) of 300 keV He + and IT1" in 150 to 300 A carbon foils, w« applied for our experiments Rutherford backscattering (RBS) for foil thick­ness calibration. Compared to earlier experiments this method offered the ad­vantage that no assumptions concerning the stopping power of thickness-calibra­ting Ions like protons »ere implied. Additionally any contamination of the tar­get could be analyzed which might have influenced the energy loss of the trans­mitted ion. The energy losses were measured by a spectrometer. Our experiments confirmed a linear thickness dependence of the energy loss. Furthermore, Indica­tion was found, that the He + particles exhibit >in increased preequllibrium elec­tronic stopping power in the first atomic layers of the solid.

Until recently the precise and well documented experiments of Skoog and Augen­licht- Jakobsson HI for 150 keV sodium ions in carbon have been taken as proof that the stopping power in thin target foils is strongly dependent on the foil thickness (fig- 1). Xn all our experiments, however, a linear dependence AE(d) was found. In order to clarify this obvious contradiction to the results in ref. HI we «transformed the stopping cross section S e of ref. HI into the original energy losses by simp' multiplying S e with the target thickness. The astonishing result of this si, jle procedure is plotted in fig. 2.

Like our results the energy losses measured by Skoog and Augenlicht-Jakobsson showed a linear dependence on d. The misleading presentation of their data was based on a not appropriate derivation of the stopping power: instead of S e ~ dE/dx the quantity 4E/d was applied. Following fig. 2 it is to be conclu­ded, that dE/dx Is constant in the range of target thickness investigated. The off-zero intercept visible in fig. 2 induced the special dependence of AE/d shown in fig. I.

In order to clearify if the off-zero intercept in experiments like in ref. Ill is due to a physical effect or simply the result of an error in calibrating the target thickness (in ref. Ill 150 keV protons were applied), an experiment had to be performed which employed a method for thickness calibration that was not ultimately recurring to energy loss measurements, too. RBS using protons for the thickness calibration of thin carbon foils seems to be the trethod that offers the highest probability of not Including undetectable systematic errors. In principle, RBS only requires accurate proton dosimetry and the accumulation

- 28 -

of the particles backscattered into a well-defined solid angle. In fig. 3 our results of the AE(d) measurements are compiled. The relative thickness scale has been constructed by RBS.

As derived from the data in ref. Ill these measurements based on a thickness scale independent of energy losses of calibrating particles also exhibit a li­near function AE(d). For both helium and nitrogen ions the extrapolated func­tion AE(d) intersects the E-axis at EX). Thus it has been established that dE/dx, i. e. the stopping power is constant in the thickness range investiga­ted. Due to the relatively large experimental uncertainty in the data points it could not be ultimately concluded, If the quantity for the off-zero inter­cept derived really was significant.

In order to reduce the experimental errors primarily the precision of the thick­ness scale had to be improved. Thus energies higher than the 300 keV available at our accelerator were indispenslble for the RBS analysis. Fortunately, there existed an experiment well suited for our purpose at the Queen's University in Kingston/Ont. With this equipment Reid and Scanlon 111 had already performed experiments to solve the Se(d)-puzzle. After minor changes in the experimental set-up the spectrometer in Kingston proved to meet the high demands involved in these investigations. As the RBS analysis was performed with protons at energies of about 1 MeV no ambiguities in background subtraction were encountered in con­structing the thickness scale for the carbon targets. The results we obtained in Kingston are collected In fig. 4.

Also these measurements confirm the relation AE • S e • d + const. As expected the quantity of the off-zsro intercept could be derived more precisely to be (600 ± 160) eV. This magnitude is small enough not to significantly falsify ion beaa applying analyses using iE - S e • d for depth profiling. On the other hand the physical foundation for the increased preequilibriuo stopping power remained still unclear.

The equilibrium stopping power of an energetic particle in a solid is given by the particle's actual charge and its dynamic screening by the target electrons. From investigations on the equilibrium charge of for example Re by Cue et al. /3/ there are indications, that at our energy of 300 keV an Impinging He par­ticle almost Instantaneously is fully stripped in the very first layers of a solid. The build-up of the dynamic screening is governed by a time constant in the order of 5 x 10-16 s e c , i„ t n e scope of the stopping cross section this would indicate an Increased preequllibrium stopping, as S e is proportional to (Zi e f f) , (Zi e f f: effective ion charge). To clarify the assumption of the pre­ceding stripping and consecutive screening an energy loss experiment employing

- 29 -

Ke , He*, and H e + + waa performed. For the construction of the (not absolute) target thlekneaa acale 300 keV protona were uaed, aa only the relative energy loaaea for the three different apeciea ware of intereat. It waa found that the three apeciea exhibited almost tha ease off-zero Intercept, thua confirming the assumption of tha early stripping.

III R. Skoog and K. Augenllcht-Jakobeeon, Radlat. Eff. 2]_ (1976) 143 11/ I. Raid and F. J. Scanion, Nucl. Instr. Meth. JJO (1980) 211 IV N. Cue, N. V. De Castro Farla, M. J. Galllard, J. C. Polzat and

J. Remlllleux, Nucl. Inatr. Meth. _170 (1980) 67

- 30 -

10 15 t tljg/cm2]

»I f 1. Stoppln« er»« aactloas for Na+-loM In carbon folia aa aaaaurad bjr Skoo« and Auiaalleht-Jakobsaoii A / .

11 U 16,

Fl». 2. «»transformation of tba .topping

eroaa aaetlona In raf. I into tha

originally aaaaurad aoargy loaaaa.

•10

«0

•50

N * — C

*0

•30

, ? • - " ' '

* .. •-"«a

;^"o2 (U 06 0.6 M> 12

'30 Ha* — C

-20 o.J" ' ' Ihicknwi

„ ^ calibration. . cgp-

'0 r r

Ofc'O * total counts • ' * EproIon

• ' ' 0 2 a.; as OS 10 13

(oil thicrin*is I r t l . units) ,

I ZOIS kV Wt-*C

X Errors in o£ «5:1 .

Errors IK d : 2-S* /

•30

:20

: . / ^ linear [ l l :

;io / aE - A ? cL+ttirt fsaii*i) leeV

/ Q5 1.0 1.5 rÜpAiMUI

Fl». 3. and 4. txpartaantll Toilfleatlon of lDeraaaad ptaaqulllbrtuii stopping powr; «nartj loaaaa of 300-k.« H+ and Ha'1* in carbon folia. Poll

• thlckniiaa aa callbratad by Rucharfoci baekacatearlng*

- 31 -

1.6. The Use of (n,a), (n,p) Reactions with Thermal Neutrons and Rutherford Backscattering (RBS) for Depth Profile and Stopping Power Measurements D. Fink, J. P BiersacK K. Tjan and M. Städele

He apply the (n,p) and (n,a) reactions with thermal neutrons for the examination of depth profiles of light «lament» In solids A/.

Samples which contain 3He, &Li, 1 0B, 1%, or 3'Cl are Irradiated with thermal neutrons of high Intensity, as obtained e.g. at the positions S-30 and S-44 of the High Flux Reactor of the ILL Grenoble. The neutrons are absorbed with kilo-barn cross sections In the mentioned nuclei and undergo nuclear reactions (n,p) or (n,a). The emitted reaction products (p,a, recoils) are reglatered by detec­tors which are facing the samples. From the energy loss spectra of the emitted particles, the depth profiles of the reacting light nuclei can be reconstruc­ted. If the proper stopping power Is known for the emitted reaction products.

Further we apply conventional RBS analysis techniques In an external cooperation for problems which cannot be solved by our technique, e.g. for measuring range distributions of Cs, Ga, Rb, Sn, Bl, Au In SI.

Implantation Profiles

Implantation profiles of light nuclei (50 - 300 keV 3He, 6 U , 1 0 B , and 1.5 MeV and N 2) in about 30 metallic and semiconducting elemental targets were

measured and found to agree well with current theoretical predictions (Monte-Carlo code TRIM) when using the latest theoretical electronic stopping powers and potentials, see figs. 1,2 111•

After high Implantation doses, the depth profiles are distorted, which can be related to sputtering and changes In the surface structure. With He concentra­tions exceeding approximately 20 at.Z, the so-called blistering effect was ob­served and studied-Organic polymer materials have gained recent interest for potential use In electronic device fabrication. Due to the extremely low sample damage of our technique, we are able to measure profiles of light Implanted projectiles and radiation damage even in highly sensitive organic polymers. In contrast to metals and semiconductors, both the range profiles and damage in polymers are found to agree with the theoretically predicted ionization distributions 74/, fig. 3. This behaviour ia in agreement with the assumption of electronic Interaction processes affecting the polymers.

Stopping Powers

The knowledge of proper stopping powers is essential for many applications in solid state physics, but nevertheless still poor for many materials. Some mea­surements were performed in order to get the proper stopping powers for protons and a-partlcles from our measured energy distributions.

- 32 -

The ('U(n, o)T reaction is particulary suitable for comparing hydrogen and helium stopping powers of the same sample (stopping ratios). Those experi­ments were performed for LiF and several Li alloys. For a detailed study of Z% oscillations in electronic stopping power, 3He, 6 U , 1 0B, 1 4 N in elementary targets between Z2 » 4 (Be) and Z% • 83 (Bl) have been studied in some detail. With a few exceptions, e.g. 3He in Bi, the theoretically predicted oscillations were confirmed /3/.

Ill J. P. Biersack, D. Fink, R. Henkelmann and K. Müller, Nucl. Inst. Meth. 149 (1978) 93

121 D. Fink, J.P. Biersack, K. Tjan and V.K. Cheng, Nucl. Instr. Meth. 94 (1982) 105

121 D. Fink, J. P. Biersack, M. Stadele, K. Tjan and V. K. Cheng, Nucl. Inst. Meth. H i (1983) 817

/4/ D. Fink, J. P. Biersack, J. T. Chen, M. Städele and K. Tjan, Proc. MRS Meeting, Strasburg, June 5-8, 1984

3 0tp1h|>jffll

Fig. 1. 3He in i r o n a 8 a n example of our range profile measurements: Comparison of experimentally determined implantation profiles (points) with Monte Carlo (TRIM) results, aa calculated (histogram) and folded with experimental detector resolution (solid curve).

Fig. 2. A nitrogen depth profile measured by (n,a) reaction in comparison with the TRIM prediction (convoluted with apparatus resolution). The large peak ex­tending from the surface to about 0.5 um depth is due to the formation of nitride and recoil implantation.

- 33 -

»' »' »*

V1

300 KEV S U * J

— » EPOXY r »"

~J 0« /^> r -r~*^f[.-. % * -*: 10' , pr \ a: • S j . »" \ Ol . **t fcl ' * - 4 '#

o t j B' » \ • - . L CO E>. « I ff =* OS W <=> •K 6^ a.

«%0 . , " w 0 .1 .2

DEPTH, JJU

Fig. 3. Implantation profile of Li In epoxy resln coapared with the TRIM pre­diction (not convoluted): Range (P) and Ionization (I) profiles-Scales: Left (Particles/100 R), reap. (MeV/100A)

Right (Li atoms/cm3).

- 34 -

2. DEFECT CONFIGURATION AND KINETIC STUDIES

2.1. Model for Self-Interstitial Trapping by Solutes C. Abromeit

Introduction

From the differences in the behaviour of the resistivity recovery of pure me­tals and dilute alloys, It has been concluded that solutes trap migrating self-lnterstltlals. Quantitative and systematic studies have yielded the Interstitial capture or trapping radii of numerous solutes in different metal solvents.

From damage rate measurements at different irradiation temperatures between 50 and 140 K, the solute capture radii were found to depend on temperature as T" 2

III. A temperature dependence is indeed to be expected when the capture rate Is governed by a drift diffusion of the interstitial in a solute-interstitial interaction potential. An elastic interaction, however, would lead to a T~1'3 dependence of the capture radius. The observed T~2 dependence would require an Interaction potential having an R - 1' 2 distance dependence, which is clearly unrealistic. The observed strong temperature dependence must have another ori­gin. A possible explanation can be given in terms of nonstationary trapping process in a discrete lattice model 111•

Description of the discrete lattice model

The interaction of the self-interstitial with a solute in regularly behaving fee metals, such as Cu, is described by a potential which allows for a number of different trapping positions characterized by different transition rates of the trapped interstitial for jumps between those traps (fig. 1). Multiple intersti­tial capture is considered in terms of a nucleatlon trap model. By choosing suitable potential parameters, dissociation of both single and multiple Inter-stitials from the solute can be accounted for. The mathematical treatment of the lattice model allows a calculation of time-dependent capture and dissociation rates as well as the occupation probabilities for the different trapping posi­tions .

The reaction rates describing the interaction of freely migrating self-lnterstitials with a given solute are introduced into a rate equation system which describes the whole defect reaction regime operating in a given irradia­ted dilute alloy.

Application' of the model to experimental results

By fitting the model to damage rate data of Cu with Au as solute 13/, capture radii, binding energies and radius Increments for multiple interstitial trap­ping have been determined (figs. 1 and 2). The model explains the observed

- 55 -

strong temperature dependence of the solute capture radii by non-stationary trapping conditions for single Interstitial» In the respective teaparature range. This non-stationary trapping also explains the unsaturable-trap beha­viour observed for oversized solutes with average nunbers of trapped lnterstl-tlals per solute up to about on«. An alternative explanation for both effects could be the subsequent dissociation (on incraaslng the temperature) of multlp-le migrating lnterstltials.

Application of the aodel to the data for Be in Cu, fig. 3 131 leads to the conclusion that the undersized solute Be form« a single-interstitial-solute complex with only one trap configuration for which stationary conditions are Instantly achieved for all the temperatures Investigated. This conclusion coincides with the picture of a mixed dumb-bell with high binding energy.

Finally, the model is applied to results of mechanical relaxation IUI and per­turbed angular correlation measurements 151 on dilute Cu-In alloys. The four different mechanical relaxation modes annihilating at 140 K must be caused by multlple-lnterstltlal-solute complexes, probably of different sizes .

The annihilation of the perturbed angular correlation signals around 80 K con­tradicts the idea that the signals are caused by trapped single interstitials.

Ill H. Wollenberger, J. Nucl. Hater. 69/70 (1978) 362. Ill C. Abromeit and H. Wollenberger, Phil. Hag. A 47_ (1983) 951. 131 A. Bartels, J. Bewerunge, F. Dworschak and H. Wollenberger, J. Phys. F JJ!

(1982) 641. /4/ K.-H. Robrock, Phase Transformation and Solute Redistribution in Alloys

during Irradiation, edited by F. V. Nolfi, Jr. (London: Applied Science), (1983) 115.

/5/ H. Deicher, G. GrUbel, R. Hlnde, E. Recknagel and Th. Wiehert, Proceedings of the Tamada Conference V on Point Defects and Defect Interactions in Hetala, edited by J. I. Takamura, H. Doyuia and M. Kiritani (University of Tokyo Press) (1982) 220.

- 36 -

Cu

C 0 N T I N U U M

0.120

>OI6o||o.l55

0.120 0.184

0.185

0.201 0.239

^ I 0*204^"z fo.zsa\ ° 3 /aissX a 4 fa. J30

capture into recovery staqe a, and a\ H„

transitions into deeper traps recovery stage

Fig. 1. Interstitial trapping by a solute atoa from the continuum by discrete juap processes (schematic). Transition energies between the configurations o^ to atj are given In eV (CuAu) •

£ 05

I Fig. 2 rate Q

. The influence of teaperature on the normalized recombination escape as a function* of defect concentration n - V/S in CuAu.

Fig. 3. The normalized recombination escape rate Q a« a function of defect concentration U - V/S for the undersized solute Be in Cu at T > 80 K. S is the solute concentration.

- 37 -

22. Effective Defect Production Rate for Pulsed Irradiation V. Naundorfand C. Abromeit

The structural aatarlal of fusion reactors will be subject to Intense pulsed irradiation. This has risen the question of how this pulsing modifies the point defect kinetics as coapared to an equivalent continous Irradiation. Pulsed irradiation aodifled defect kinetics has been treated recently /1-V describing defect concentrations by well known rata equations /5,6/. Fro« the­se treatments it was concluded that tha mean defect concentration for a pulsed Irradiation should always be smaller than the defect concentration for a cor­responding continuous irradiation with the time averaged production rate <Kp>.

He give an analytical proof for the above conclution by introducing an effec­tive defect production rate Kgff /7/. When Kgff is used In connection with the appropriate rate equations, mean defect concentrations are evaluated, with the average taken over the periodicity of the pulsed production rate. Furthermore an analytical expression is deduced for K,ff for a wide range of point defect parameters.

We separata the fluctuating defect concentrations Cj v (1 means interstitial, v means vacancy) under pulsed Irradiation into mean defect concentrations <Ci y> and periodic fluctuations f^ v with zero mean according to the relation

Ci.v - < C i > v > + f i p V (1).

Considering first order reactions (rate constants K^, Ky) and recombination reactions (rate constant K i > T ) yields

Keff " < V " Kiv(Kv <fv 2 j > + K 1<f 12>)/(K 1 + K^) (2).

An analytical expression for the relative reduction of the effective produc­tion rate ÄK eff/<K p> - (<Kp> - t^H)/<Kp> has been derived for the case, that the pulsing frequency is higher than the annealing rate of the slower moving defect. A representative result is given in fig. 1. It shows that under certain conditions, i.e. predominant recombination, mean defect concentrations are con­siderable lower than those calculated from mean production rates *»Kp>.

Ill 0. J. Diene«, Rad. Eff. 36 (1978) 101. III K. Krishan, Rad. Eff. _45 (1980) 169. IV H. Gurol and H. H. Ghoniem, Rad. Eff. 52. (1980) 103. IUI N. H. Ghoniem and H. Gurol, Rad. Eff. 21 (1981) 209. 151 R. Sizmaim, J. (fuel. Mat. 69/70 (1978) 386. 161 C. Abromeit and R. Poerschke, J. Nucl. Mater. J52 (1979) 298. Ill 7. Kaundorf and C. Abromeit, Rad. Eff. 69 (1983) 261.

- 38 -

M

10°

10-'

io-2

io-3

l v i o - 4

io-5

io-7

. / I ' Ki+Kvi<C„> / . I

• i '

10"8 10"7 10"6 10"5 10"* 10"3 10"2 10~1 10*° T / T -

Fig. 1. The relative reduction of the effective production rate 4Keff7<KB> as a function of T/T (T 1* the duty cycle time and T the periodicity of K„). • Numerical Integration result•, analytical solutions. Parameters: A: K,! - 10* sec-1. Ki - 1 sec-*, K, - 10" 2 «ec'l; <Kp> - 10"2 x t/T sec~l, u - A sec - 1- B: K l v - 8 x 10 1 2 sec - 1, Ki - 4 x 10 8 sec - 1, Kj - 10* sec-!, <Kp> - 3 x 10 - 2 XT/T sec - 1, u « 2» x 10* sec~l.

- 39 -

2.3. Localization of Displaced Impurity Atoms in Irradiated Aluminium Alloys from Channeling Experiments M. Müller

In order to understand the diffusion phenomena In Irradiated alloys knowledge of the basic processes especially of the atomic transport mechanism is neces­sary. The Irradiation induced defects react with the substitutional^ soluble Impurity atoaa by fornation of defect complexes, which enhance or delay the diffusion process or sake it even possible. The structure and dynamics of these defect complexes have to be studied In siaple materials like AI, N1 or Cu, the physical properties of which are well-known.

The configuration of defect coaplezes in metallic single crystals can be de­termined by using the channeling aethod. The Interaction of tne channeled Ions with the lapurlty atoa In defect coaplexes results iu backacattered ions, nuclear reaction products, or inner shell X-rays. The yield of these processes Is measured for various crystallographic directions of the target relatively to the beam direction. In order to determine the impurity atoa displacement the ex­perimental yields are coapered with theoretical values, obtained fron calculated flux distributions of the channeled Ions.

The channeling process was simulated In a Monte-Carlo-prograa based on Che bi­nary collision model (BCM)• The trajectories of the channeled particles are obtained by calculating In momentum approximation the collisions of the ion projectiles with the actual nearest target atom. The computation took care of the vibrations of the lattice.atoms (simulated by normally distributed displace­ments), impact paraaeter dependent electronic energy loss and multiple scat­tering of the projectiles by the crystal electrons. Energy- and flux distribu­tions of channeled particles for <100>, <U0>, <111> axial and { 100), { U0}, {ill} plana- incident beams are shown in fig. 1 and fig. 2. The theoretical

>. yield of backscatteied ions has been obtained by using the flux-dlstrlbutions and assuming - <100>, <110> or <111> displacement of the Impurity atom In the defect complex (e.g. mixed dumbbell, In which an Impurity atom and a self-in­terstitial atom share one lattice site).

A check of the computer program and its assumptions was performed by calcula­tion of the theoretical yield from matrix atom« (the concentration and posi­tion of which is accurately known) and comparing this yield with the corre­sponding aeasured host atoa value. Froa aeasured angular scans in diluted alumi­nium alloy single crystals (Swanson and coworkers [1973 - 1983]) aligned yields 7min and the half widths *i/2 of the host atom dips were extracted. Fairly good agreement with the calculated values could be found (Tab. 1). Since the devia­tions are systematical they are presumably caused by amorphous surface layers on the target resulting in an increase of the beam divergence. The discrepancies in *l/2 can be easily reduced, it the position of the tilting plane Is accurately taken Into account, which Is not indicated in the description of the experimen-

- 40 -

tal detail». Comparison of <100>, <110>, <111>, (lOOj, or {ill} aligned yields measured by backscatterlng of He* from Impurity atoms with the corresponding theoretical values is shown in Tab. 2. The best fit to the experimental data has been obtained by assuming the Impurity atom In the defect complex to be displaced in <100> or <111> direction with more than 0.1 nm out of the lattice site. A clear decision between the <100> and the <111> mixed dumbbell configuration, how­ever, could not be made, even not by evaluation of angular scans (see fig. 3).

Ill M. Hüller, HMI-Bericht (1984) to be published. Ill H. Miller, duel. Instr. Meth. 213 (1983) 453. /3/ M. L. Swanson and L. M. Howe, Hucl. Instr. Meth. 211 (1983) 613.

<100> <110> < m > Fig. 1. Calculated equl-flux contours of 1 MeV He + in <100>, <110> or <111> channels of aluminium at 40"K. The laolines represent flux densities of 10 X, 20 X, 50 X, 100 X, 150 X, 200 X, ISO X, 300 X, 350 I, 400 X and 450 X (increasing with increasing distance from the lattice site and normalized to randomly distributed projectiles). a 0 » lattice constant.

0. 0.5 1. Fig. 2. Normalized flux density of I MeV He + ions channeled in { 100} { 110} or (ill) planes in aluminium at 30 K. Tilt angle to the <110> direction: 6*; d„ la the spacing between the lattice planes; x is the distance to the lattice plane.

- 41 -

Al/O. 09«t7iMn after irradiation with 0. SMeV He +

2 to a fluenc« of 7.0E15 cm at 7OK

Fig. 3. Comparison of experimental and theoretical normalized yields for an <1110> angular scan in Al/0.09 at.Z Mn for backseattering of 1 MeV He ions at 30 K (beam divergence At - 0.05', depth increment 50 - 150 na). The marks cor­respond with experimental yields /3/. The asymmetric scan was obtained with the target tilted 0.2" from <110> alignment. The curves are calculated for different fractions of displaced Impurity atoms (in steps of 0 Z, 10 Z, 20 Z

70 Z)i

a) in <100> direction with a displacement of 0.14 nm (<100> mixed dumbbell) b) in <U1> direction with a displacement of 0.28 nm (<111> mixed dumbbell).

The left curves show the deviations caused by a misalignment of 0.15" - 0.2" from <110> and a variation of the tilt plane between 2.5* - 4.5" from the (2U( plane.

- 42 -

Tab. 1. Comparison of experimental and theoretical aligned yields and half widths of 1 MeV He + in Al-alloy-single crystals at 40 K.

exper imenta l Monte-Carlo- calcula t ion

Ynin • l / 2 Ym-in * l / 2

aoo> 0.02 1.32 - 1.42- 0.020 1.40

<U0> 0.015 1.65 - 1.89 0.014 1.84

<111> 0.06 0.89 - 1.25 0.051 1.10

(100) 0.26 - 0.235 0.28

(110) - - 0.292 0.20

(111) 0.240 - 0.187 0.33

Tab. 2. Normalized axial and planar yields of He + ions backscattered from im­purities in He + irradiated Al-alloys (measured by Swanson and coworkers: refe­rences see A / ) and BCM computed <10C* and <111> displacements s in nm. a) <100> displacement of the impurity atom analytically calculated by the authors of the measurements, c) axial <in> aligned yields.

y<ioo> r(iio> y{ioo) y{iii) soooy s-(iii)

Al/0.13 at.% Cu 0.148 ' 0.136 0.691 0.140-0.144 0288-0.298 (100) and (110) scan 0.150-0.162 0291-0.302

Al/0.10 a«.S Ge 0.I0O-0.U6" 0230 0.280 0.106-0.110 0249 (100) and <110> scan 0.094-0.108 0249 0249 0253 0.098-0.104 0239 0291 0.315 0.106-0.108 0249 0.544 0.360 0.124-0.128 0263-0266

0288 0.480 0.565 0.110-0.124 0259-0.263 0.286 0.400 0.461 0.122-0.132 0256-0266

AI/0.12 at.« Zn

AI/0.09 aL* Zn

0.100* 0213 0.403 0.120-0.130 0253-0263 0.456 0279 0.128-0.134 0266-0277 0.350 0.435 0.670 0.122-0.128 0263-0.273

Al/0.09 alft Mn 0.141-0.149' 0.320 0.320 0.134-0.142 0280-OJ39

0.129 0.523 0 2 6 5 ' 0.134-0.136 0284 0.149 0.702 0275« 0.138-0.140 0287-0291

0.880 0.450' 0.136 0287 0.590 0.450« 0.128 0270

Al/0.08 « . * Ai 0.123-0.130« 0225 0241 0.114-0.122 0263-0266 0218 0.359 0.114-0.122 0263-0266

0.318 0384 0315 0.118-0.128 0260-0278 0.488 0.484« 0.124 0242 0.460 0.440' 0.124 0249

- 43 -

2.4. Lattice Location cf Impurity Atoms Studied by X-ray Excitation with Channeled Ions KH. Ecker

To Investigate defect Impurity complexes In dilute alloys at low temperatures facilities have been set up to determine the location of impurity atoms with channelling techniques. In addition to Rutherford backscattering and ion indu­ced nuclear reactions, the methods mostly used so far to detect the impurity atoms, Particle Induced X-ray Excitation (FIXE) was established to enable the study of light lapurltles in a heavy matrix.

Ho(Co) single crystals were prepared by Ion implantation and subsequent annea­ling to yield average Co-concentrations of order 10"3 in a layer about 300 na *t the surface with most of the Co atoms located on substitutional lattice si­tes. After Irradiation with 600 keV protons at 50 K channeling measurements re­vealed a considerable fraction of the Co being displaced from substitutional to Interstitial sites, due to the.trapping of Mo-lnterstitial atoms, that are mobile at the Irradiation temperature. To determine the location of the disp­laced Co atoms experimental x-ray excitation yieldB I.e. <111>, <110> and <100>-axial angular scans were compared with theoretical yields calculated on the basis of detailed Monte-Carlo computer simulations for the flux of channeled protons.

At low irradiation fluences all experiments are compatible with the predomi­nant formation of a single configuration where the Co-Impurity is displaced by 0.105 no Into the <110> - direction (fig.1). Other configurations thought pos­sible In a bcc-lattice like octahedral- and tetrahedral-position as well as <100>-tind <lll>-dlsplacement can be ruled out by the experiments. At higher fluences an additional configuration can be resolved with a 0.14 nm displacement into <100>-direction that is not far from the octahedral site. The observed dependence of the displaced fractions on the irradiation fluence can well be explained by the unsaturable trap model If the <110>-displscement is assigned to the trapping of a single interstitial to form the so-called <110>-mixed dumbbell and if the dis­placement into the near octahedral position is associated with the trapping of two interstitials. A fit to the probabilities Pi and P2 for the trapping of one and two interstitials in the unsaturable trap model (fig. 3) yields a ratio of the trapping radii of Co-trap and vacancy r t/r v - 0.1 ± 0.03 and a production cross section fo D - (2.6 ± 0.3) 10~ 2 0 cm2 for freely migrating interstitials. Thus with a displacement cross section On - 1.5-10-1' cm2 for 600 keV protons In Mo the fraction of Interstitials escaping close pair recombination at 30 K cal­culates to f • 0.17. The values obtained for r t/r v and f are in fair agreement with the results of MSssbauer studies by Harangos and coworkers. However the number of possible configurations and their assignment to the trapping of one or more Interstitials remains controversial.

K. H. Ecker, J. Nucl. Mater. 2i£ (1983) 301 K. H. Ecker, Nucl. Instr. Meth. JI2 (1984) 747 J.. Marangoe, W. Mansel and G. Vogl, suuoltted to Rad. Eff.

- 44 -

Flg. 1. Comparison of experlnental with calculated angular dependence of the normalized reaction yield. Experlnental yield after irradiation with 3.1016 cn-2 proton« of 600 keV at 50 K. The curves are calculated assuming that a fraction of 0 X Increasing In steps of 10 X up to 50 Z of the Co atoms are displaced by 0.105 nm into the <110>-directlon.

Fig. 2. Angular scans of experimental Co-Ka X-ray yields after irradiation at 50 K with 8-1016 cn-2 p r o t o n s o f 6 0 0 KeV compared to calculated yields assuming -.-.-. all Co substitutional 25 Z in the <110>-split configuration, 5 X in near octahedral configuration, both configurations combined.

- 45 -

T 1 r n j p j j -

.U

Cf ~ 2 x 10"3

^J^4

<111> A 4

<110> o • <100> D "

J I [ I 1

e 0 1 2 3 A 5 6 7 8 9 € »10 1 6

0 [cm-2] ••

Fig. 3. Fluence dependence of the displaced fractions In the <110>-spllt (open symbols) and near octahedral position (filled symbols) compared to the proba­bilities Pi and ?2 f o r t h e trapping of 1 and 2 Interstltlals in the unsatura-ble trap model-

- 46 -

2.5. The Lattice Positions of B in Si at High Implanted Doses and Annealing Temperatures D. Fink, J. P. Biersack andK. Tjan

From Che angular dependence of Che emission yield of Che reaccion products afcer the B(n,ot)7Li reaction with chennal neutrons, Che latcice posiclon of lighc Impu­rities in single crystalline samples can be derived /l/. If the emission yield (as a function of Che observed angle) exhibica a maximum, we have a channeling effect - in case of a minimum, we observe a blocking effect. The measured com­bination of channeling and/or blocking structures In different direcCions Indi­cates whether the impurity is situated on an interscitlal or substitutional site, and Che shape of the channeling (reap, blocking) peaks gives addicional decails, as e.g. Che magnitude of Che displacement of Che impurities from the laccice sice.

The application of Che (n,a) speccromecry has Che' advantage Co be destrucclon-free, which is of high Importance for sensicive cryscal structures, as Si. The measuring time per sample is hcwever long (usually more than one reactor cycle), due to the high angular resolution required in this case. Our experimental setup at the ILL is unique, Insofar as It uses 2 mulcidetectors of 100 sensitive areas each.

Laccice posicion determinations were performed mainly for B in Si, lmplanced at high doses, due Co Che praccical importance of chis system. Various posi­tions are found for boron during the transition from purely substitutional to random sites. B has the tendency Co cluscer as B2 or B3 per Si unic cell ac high doses afcer high Cemperature annealing and slow cooling, in contrast to laser annealing (fig- 1) 111 •

l\l J. P. Blersack, D. Fink, J. Lauch, R. Henkelmann and K. Hüller, Nucl. Inst. Meth. UJ8 (.1981) 411

111 D. Fink, J.P. 3iersack, H.D. Carscanjen, F. Jahnel, K. Müller, H. Ryssel and A. Osei, Rad. Effects 77 (1983) 11

Fig. '. Silicon laccice (open circles) with B clusters consisting of either (a) two (B2) or (b) three (B3) atoms (closed circles), respectively. The dis­placements of the B atoms are indicated by arrows and correspond along <111> to about cvice Che experimental values o, 0.158 - 0.01 A.

- 4 7-

3. THERMAL AND IRRADIATION ENHANCED DIFFUSION

3.1. Thermal Diffusion of Cobalt and Nickel in Copper ft Döhl, M.-R Macht and V. Naundorf

The dlffusivity of cobalt and nickel In copper has been measured recently by classical sectioning techniques at temperatures above about 0.7 of the melting temperature T„ of copper /l/. In the case of cobalt diffusion a slight curva­ture in the Arrhenius plot was observed, which was attributed to the short circuiting effect of randomly distributed dislocations. This effect, however, becomes notice»ble only if the total diffusion length of the Impurities is lar­ge compared to the mean distance of dislocations. Whereas in tint earlier mea­surements this condition was fulfilled, the recently developed sputter sectio­ning technique allows resolution of diffusion lengths shorter by more than three orders of magnitude than these resolved by classical sectioning techniques HI and shorter than the mean distance of dislocations.

In the present investigation diffusion coefficients were measured with a com­bination of sputter sectioning and secondary ion mass spectroscopy (SIMS) on carefully designed specimens between 0.47 T m and 0.63 T m 13/. These specimens were plain single crystals of pure copper with an inserted thin layer of co­balt or nickel in a well defined depth. They were prepared under UHV condi­tions by sputter deposition of the tracer onto the smooth surface of the sin­gle crystal and subsequent vapor deposition of copper onto this layer I hi. The dislocation density of the single crystals has been estimated by etchpit coun­ting to be 10 6 - 10 7 cm"2.

Specimens were annealed in a vacuum better than 10~* Pa, temperature was con­trolled by calibrated Pt/PtRh thermocouple and held constant to within 0.5 K. In-depth profiling of the unidirectional diffusion gradients was done with a commercial SIMS (Atomika), using 4 KeV 02+ sputter ions. Depth resolution of this sectioning technique was about 10 nm /4/. The background signal was suf­ficiently low to resolve about 10 ppm of the tracer atoms during profiling. The absolute depth scale for the tracer profiles was provided by mechanical probe or optical Interference method after sectioning was completed. The depth scale error was about 10 Z. Figs. 1 and 7. give examples of diffused Ni-and Co-sandwich samples. The diffusion coefficients of Ni in Cu were evaluated in the entire temperature range from penetration plots similar to fig. lb by use of the thin layer solution of the diffusion equation. Such plots were ob­tained also for the diffusion of Co in copper at temperatures above about 750 K. Below this temperature, due to the limited solubility of Co in copper and in­sufficient annealing tices penetration profiles as given in fig. 2 developed, which are described by a complementary error function. No indication of short circuiting effect has been found in any penetration curve. All measured diffu­sion coefficients are compiled in the Arrhenius plot of diffusion coefficients vs. reciprocal temperature (fig. 3). The error bar of these values is about 30 %• In addition high temperature data of Mackliet III are given. A fit of

- 48 -

the data to an expression of Arrhenlua type, I.e. D • D 0 exp (- Q/kT), yields paraneters D 0 and Q as given In table 1. Obviously for both, Ml and Co, a high and a low temperature branch has to be distinguished, which meet at about 1000 K.

The good linearity of the Arrhenlus plots below 1000 K and the absence of dis­location short circuiting effects at these temperatures leads to the conclu­sion, that true bulk diffusion was measured up to about 1000 K. The slight curvature of the Arrhenlus plots above 1000 K should therefore discussed ei­ther as a certain temperature dependence of the parameters D 0 and Q or more likely as contribution of an additional process, e.g. diffusion via dlvacan-cles.

Ill C. A. Mackllet, Phys. Rev. _109 (1958) 1964 111 K; Maler, phys. stat. sol. (a) 4± (1977) 567 13/ R. DShl, M.-F. Macht and V. Naundorf, submitted phys. stat. sol. (a) HI M.-P. Macht and V. Naundorf, J. Appl. Phys. 5i3 (1982) 7557

Table 1. Diffusion parameters of nickel and cobalt In copper.

D 0 ( c m / s e c ) Q (eV) N i -<• Cu 2 . 7 2 . 4 6

0 . 7 6 2 . 3 3 Co •* Cu 1 . 9 3 2 . 3 5

0 . 5 7 2 . 2 3

temperature range (K) 1O00 - 1350 6O0 - 1000 1100 - 1350 680 - 1100

' 1 r

= I \ a i

i * »r

>-t :

s •: K 5 ~ • AS PREPARED

5 • -a • • M

~ • =t • ' i I J l l f FUSED

.

^ bl -j^^OIFMSll -1 X 1 A. •

i "V .

.

-100 2D0 Dm* liwl .><->•

Fig. 1. SIMS depth profiling of a Cu-Ni sandwich specimen, a) Monoatomlc Ni layer *s prepared and as broadened by diffusion, b) plot of fig. la In the form of logarithm of intensity vs. depth squared (the depth of the maximum is taken as x » 0).

- 49 -

0.1 1 ' — • 1 1

* ^i : « •

2 ? * •X

»-2 fct -w s

s '• T.743«, tOJh

• w i •

u- V^ 100 150 200 250 »ln«l

Fig. 2. Broadening of a monostotic Co layer In Cu after diffusion. The solubi­lity limit of Co In Cu Is Indicated by the sudden change of slope at about 100 no.

KT

KT"

10-'

£ KT"

§ £ W*

K T 1 8

w™

• • present work O A Mocklie»

Fig. 3> Temperature dependence of the thermal diffusion coefficient of cobalt and nickel In copper In the Arrhenlus plot.

- 50 -

3.2. Radiation Induced Diffusion of Be, Mn and Ni in Copper H.-J. Gudladt, M.-R Macht and V. Naundorf

The kinetics of precipitation and phase transformation In alloys under Irradia­tion Is Investigated because of Its practical relevance on the development of structural materials for advanced reactors. In this respect are of particular Interest the rates of atomic redistribution and the development of precipita­tions In solid solutions. Quantitative Information on the kinetics of these pro­cesses can be drawn from measurements of partial diffusion coefficients of the solutes.

The method of diffusion coefficient determination has been described elsewhere /l/. It is performed on single crystals, which contain an approximate monolayer of the solute in such a depth under the surface to ensure an undisturbed regime for the solute under the applied 300 keV Cu + self-ion irradiation. Depth profi­les of the solute before and after irradiation were taken by dynamical SIMS, i.e., continuous sputtering off the sample material through the diffusion pro­file and simultaneously analyzing by secondary ion mass spectrometry. The con­centration profiles have been measured down to about 10 ppm solute concentration with a depth resolution of about 10 nm.

From the depth profiles in the irradiated zone the diffusion coefficients under Irradiation have been evaluated. The diffusion coefficients for the solutes Be, Mn and Ni are plotted in an Arrhenlus diagram in fig. 1 for a defect production rate k 0 • 8 x 10~* dpa/s (ion current density 1 uA/cm ). Thermal diffusion coef­ficients are also given in fig. 1. The efficiency factors n v

8 0-'- u t e « Dsolute*Cu/DCu*Cu d e r i v e < i from the thermal diffusion experiments yield the following results:

n vN i - (3.5 ± 1.7) * exp [-(0.26 ± 0.05)ev/kT]

Tiv"" - (10 ± 4) * exp [-(0.04 ± 0.05)eV/kT] n v

B e - (8 ± 3) * exp [-(0.00 ± 0.04)eV/kl]

The long range diffusion coefficient D j r r of the solutes under irradiation may be described by three contributions, Di r r - IVi x + DSJ + Ds v, where DJ^J presents the athermal atomic mixing effect due to the direct recoiling by the irradia­tion particles and D s^, D S v the diffusion of the solute via interstitials and vacancies, respectively•

Daix has been estimated to be about D ^ - 10-13 x k ( ) Cm2/sec, where the produc­tion rate k 0 of freely diffusing defects Is inserted in units of sec - 1 121.

For the solute diffusion via interstitials two limiting cases have to be dis­tinguished, namely i) the case of negligible interstitial solute binding and 11) the case of strong interstitial solute binding. As irradiation induced point

- 51 -

defects annihilate at point defect sinks the solute transport by complexes yields solute segre-gatlon at these sinks. The solute atoms have to be released in order to become mobile again. In the case of heavy Ion or neutron irradiation the release Is achieved by collision cascades. The diffusion of fast diffusing interstitial solute complexes over distances larger than the mean sink distance is determined by the release rate k r of solutes from point defect sinks of con­centration c 9. The adequate diffusion coefficient is then given by 121 DSi " kyfl/AnrgCa where tl is the atomic volume and r, the annihilation radius of sinks. In the case of negligible interstitial solute binding, the diffusion coefficient is simply given by M/ Dgj » n^D^Ci, where Dj Is the diffusion coef­ficient of the solvent lnterstitials of concentration c± and ni is an efficiency factor.

In analogy to the weak binding case for interstitlals the diffusion coefficient Dg v of solutes via vacancies (v) is given by Ds v » n vDv cv The efficiency fac­tors n v for the various solutes are those derived from thermal diffusion experi­ments. The temperature dependence of the diffusion coefficients will be inter­preted as follows.

Diffusion of Ni in Cu: Because of the low vacancy efficiency factor n vN 1 the

diffusion of Hi via vacancies plays a negligible role under irradiation. As no indication of complex formation has been found, the diffusion coefficient un­der irradiation Is written as D j r r - niDiC^ + Dgj.x. At temperatures above 450 K the diffusion must be assigned mainly to interstitial transport with an efficiency factor m~l. For lower temperatures the significance of irradiation Induced defects decreases as given by the calculated curve In fig. 1. At and below room temperature the atomic mixing effect dominates the transport leading to a temperature independent diffusion coefficient of about 8 x 10 - 1? cm2/sec in the present case.

Diffusion of Be and Mn: For both solutes diffusion out of the irradiated zone was observed 151. This has to be Interpreted in terms of interstitial-solute complex formation and migration. In this case the diffusion coefficient under Irradiation Is given by 0±TT - kjfl/torgCg + n vD vc„ + O^x- Below 450 K, the diffusion of interstitial complexes to and the release from defect sinks domi­nates the diffusion, 1. e., the first term of the sum is the leading term. For the solute Be the release rate k r ~ k 0, yielding at room temperature D i r r

B e " 6 x 10~ 1 6 cm2/sec. This value is significantly higher than D,^. The lower value of the diffusion coefficient for Mn, D l r rMn . 2 x 10-16 Cm2/sec is probably due to a slightly reduced release mechanism. Because of the high vacancy efficiency factors n v for both solutes at temperatures above 450 K, the diffusion coeffi­cient may b* influenced by the vacancy contribution t)vDvcr.

- 52 -

Ill M. P. Macht and V. Naundorf, J. Appl. Phys. £3 (1982) 7531. Ill M. P. Macht, V. Naundorf and H. Wollenberger, J. Nucl. Mater. 103/104

(1981) 1487. 131 V. Naundorf, M. P. Macht, H.-J. Gudladt and H. Wollenberger, Proc. Yamada

Conf. V on Point defecti and defect Interaction* in metala, eds. J.-I. Takanura, M. Doyaaa and M. Kirltanl, University of Tokyo Press, 1982.

HI R. Sizmann, J. Nucl. Mater. 69/70 (1978) 386.

10 •15

- <& ^ 10

10"-

A BE • MH

c A * c i D i

in • io3 [r 1]

Fig. 1. Arrhenius plot of diffusion coefficients measured for ky, _ 8 x 10"* dpa/sec. Straight solid lines give the thermal Impurity diffusion. The calculated stationary defect diffusion In copper Is indlcsted by CyOy - ciDj.

- 53 -

3.3. Fast interstitial-Solute Complex Diffusion under Irradiation in CuBe H.-J. Gudladt, V. Naundorf and M.-R Macht

The long range diffusion of mobile Interstitial solute complexes Is limited by defect sinks» At such sinks, the Interstitial configuration annihilates leaving the transported solute immobilized at the sink site. If diffusion is observed over distances larger than the mean sink spacing, the segregated atoms have to be released from th* sinks in order' to become mobile again. In tie case of heavy Ion or neutron irradiation release may be achieved by collision cascades. As a consequence the resulting long range diffusion la not solely governed by the mi­gration enthalpy of the complexes, but also by the release rate from sinks. This leads to an effective diffusion coefficient, which is smaller than that of free diffusion. Recently irradiation Induced diffusion coefficients of Be in Cu have bei-n analysed in terms of the above considerations /l/. In the case of self ion irradiation the damage is restricted to the projected range of the ions. Com­plexes formed in this region can diffuse into the undamaged matrix. There they anneal out at point defect sinks and therefore the solute atoms will be distri­buted according to an absorption profile with an absorption (decay) constant a, which is related to the actual sink concentration c s in that region as o »

<*• rms es/ n) 1 / 2

ill• Here r m s Is the capture radius of the sinks and Q the ato­mic volume. Investigation of the redistribution effect of Be in Cu /2/ was performed on single crystalline copper specimens with inserted thin layers of Be. The pre­paration of such specimens has been described in detail elsewhere /3/. Irra­diation experiments were performed with 300 keV Cu+ions at temperatures between 295 K and 700 K. Depth profiles of the Be concentration were recorded by secon­dary ion mass spectroscopy (SIMS) before and after irradiation.

Fig. 1 shows depth profiles of Be as measured with SIMS before and after irra­diation. After irradiation the Be peak has been broadened substantially and furthermore Be is detected beyond 200 nm, a depth much larger than the projected range of the damaging Cu+iona. The long range tail of the Be distribution emerging into the non-irradiated part of the specimen seems to obey a simple exponential. The reciprocal slope (decay constant) of these absorption curves are nearly temperature independent below 500 K and exhibit no significant depen­dence on Irradiation time or dose rate, which both were varied by about one order of magnitude (fig. 2).

From the fact, that at room temperature Be has diffused about 100 nm into the crystal, a migration enthalpy for the Be atoms of less than 0.65 eV is dedu­ced. The binding enthalpy of the Be-lnterstitial complex is estimated to be about 1.3 eV. From the magnitude of the decay constants between 300 K and 500 K a concentration of point defect sinks of about 4 x 10"7 per atom is imp­lied, which is more than one order of magnitude smaller than found in the da­maged region /!/.

- 54 -

/I/ V. Naundorf, M.-P. Macht, H.-J. Gudladt and H. Wollenberger, Yamada Conference V on Point Defects and Defect Interactions In Metals, Kyoto, Japan (Nov. 1981) 934.

Ill H.-J. Gudladt, V. Naundorf, M.-P. Macht and H. Wollenberger, J. Nucl. Mater. Uj[ (1983) 73.

/3/ M.-P. Macht and 7. Naundorf, J. Appl. Phys. 53 (1982) 7551.

200 300 DEPTH Iran]

Fig. 1. Depth profiles for a single crystalline layer specimen prepared with a 0.05 pg/cm2 Be layer at 65 nm- 0 : before Irradiation; t : irradiated with 300 keV Cu + Ions at 295 K. The production rate of freely migrating defects was 7 x 10" 3 s - 1.

«lO'/TIK-'l

Fig. 2. Temperature dependence of the decay constant for defect production rates k 0 between 8 x 10~* and 7 x 10"3 « _ 1 and irradiation tines t between 1 x 10 and 1.1 i lO* i (Indicated by different symbols).

- 55 -

3.4. Diffusion in Austenitic FeCrNi and in Ni under Irradiation A. Müller, M.-P. Macht, V. Naundorf and R. V. Patil (BARC Bombay, India)

The mlcrostructure of alloys Is altered considerably by Irradiation due to en­hanced diffusion and redistribution of the alloy constituents. In particular It has been shown, that in stainless steels, which are candidates for fusion reactor materials, under irradiation non equilibrium nickel-silicon phases are precipitated and that this is strongly correlated with the swelling behaviour /l/. To get a fundamental understanding of these phenomena, it is essential to investigate the diffusional properties of major and minor constituents of such alloys. In particular the role of point defect sinks has to be investigated, which are produced by the irradiation Itself and which can alter diffusional af­fects considerably. The latter can be done by performing self diffusion experi­ments under self ion simulation irradiation, which is known to produce enhanced sink concentration 111.

Direct measurement of diffusion coefficients 13 accomplished with dynamical SIMS on specimens of sandwich type, which contain a thin layer of the relevant tracer atoms (SI and 63lli) in a well defined depth beneath the surface /3/. The alloy specimens were produced by sputter deposition at room temperature in ultra high vacuum. The sputter deposition technique yielded alloy samples with good surface and sufficiently low content of structural defects like disloca­tions-Sandwich samples of Ni and austenitic Fe-20Cr-20Ni with Inserted layers of Si and *^N1 were irradiated with 300 KeV Hi + ions with a current density of

2 1 uA/cm • The self diffusion coefficients of nickel are given in fig. 1. Analy­sis of these values by means of simple rate equations, taking into account the production of single vacancies and lnterstltials, their mutual recombination and their annihilation at fixed 3inks allow the evaluation of the sink concentra­tion. An upper limit of about 4 x 10~° per atom for the effective sink con­centration has been estimated. This value is about one order of magnitude lower than that found recently on self Ion irradiated copper /2/. In the alloy speci­mens the diffusion coefficient of nickel at 900 K was estimated to be about 6 x 10~16 c a /sec, which is about one fifth of the Ni self diffusion under the same irradiation conditions. For silicon the diffusion coefficient in this alloy was about 7 x 10 - 15 c m /sec, i.e. one order of magnitude larger than the Mi-diffu­sion (c f. fig* 1). This result is in accordance with the observation that in FeCrNi alloys under thermal conditions nickel is the slower moving species and silicon diffuses faster /l/. Furthermore this supports the interpretation /l/ that the Nl-Sl phases, which are observed under irradiation, a;e formed by a flux of fast diffusing Si-defect complexes to point defect sinks and segrega­tion of NI at these sinks by the Inverse Klrkendall effect.

- 56 -

Ill F. A. Garner, Proc. Symp. on Phase Stability during Irradiation, J. R. Holland, L. K. Hansur and D. I. Potter Edc. The Metallurgical Society of AIME, 1981

111 M.-P. Macht, V. Naundorf and H. Wollenberger, J. Hud. Mater. 103/104 (1981) 1487

131 M.-P. Macht and V. Naundorf, J. Appl. Phys. 5i (1982} 7551.

10 -13

10 - « •

10 -«

Ni,therm.

300 kV Ni'

• Nl - * N i

A SI -»FeNICr

• Ni -*FeNiCr

i I

2 . 0

1 / T ( 1 0 " 3 K"-*)

Fig. 1. Tenperature dependence of the diffusion coefficients of Hi" in Ni and of Si and Ni* in Fe - 20Cr - 20N1 under 300 keV Ni + irradiation. Current density 1 pA/cm . Fit of a simple rate equation model to Nl* + Ni values is indicated by a straight line.

- 57 -

Short Range Ordering Kinetics in Electron Irradiated a-Brass C. Abromeit and R. Poerschke

In the a-Cu-Zn system numerous Investigations of the electrical resistivity changes due to short range ordering (SRO) have been performed after thermal treatment and after Irradiation. Recently the equivalence of the Zener relaxa­tion and the electrical resistivity method under thermal vacancy conditions has been demonstrated 111. However, discrepancies between the results of the two methods have been claimed to exist for the corresponding irradiation experi­ments 111. To answer "-.he question whether the above comparison is reasonable because (1) for the Zener relaxation experiments the electron flux density and (11) the residual Impurity content were by two orders of magnitude lower than for the resistivity experiments, the electrical resistivity of an a-CuZn alloy containing 30 at.Z Zn has been measured on-line during 3 HeV electron irra­diation at temperatures between 299 K and 435 K. Identical sample material and irradiation conditions are used to achieve results 111 which are well suited for the comparison with the Zener relaxation results of Halbwachs et al. Ill• From the measured resistivity changes thi. relaxation rate T~1 for the shore range ordering process due to vacancies and interstitials could be evaluated by the empirival law for the resistivity kinetics

-p - K (p - p ) y • T-l (1)

The constant K is related to the total number of jumps per atom which is needed for the transition between a completely disordered and the completely ordered state. The determination of the resistivity kinetics is simplified if T does not change with time during the measurement. Then equ. (1) can be easily integrated -For T > 393 R and t > 1000 sec stationary defect concentrations have been de­rived from Zener relaxation measurements HI• In the same temperature range the present data are found to be well described by equ. (1) with 0.8 < T < 1.2, i.e. with an exponential kinetics and a fairly narrow distribution around a single relaxation time. Also at temperatures below 393 K, at which stationarity has not been checked explicitly, the experimental data follow an exponential law approximately.

For a quantitative comparison of the present data with those from the literature 11 *> i /2,4,5/ all data were normalized to E - 2.5 MeV and d*/dt - 4.7- 10 cm-'1 s - i,

i.e. to the Irradiation conditions of the Zener relaxation experiments according to Halbwachs et al. /2/. For the normalization the relation T-1 ~ (dt/dt)0.5 a n <j T~ (E)/T-l(E0)a In E/E0, have been used. In fig. 1 an Arrhenius plot of the nor­malized data is shown.

Firstly the relaxation rates are compared with the calculated atomic jump rates. For the calculation a simple defect reaction model has been assumed: Frenkel

- 58

pairs, I.e. vacancies and lnterstltlals are homogeneously created with a con­stant production rate and they annihilate either.' by recombination or at sinks. Obviously for T > 325 K excellent accordance between the calculations with a sink density 6 - 1.5«10 cm"2 and the present data Is observed. Below 323 K the experimental data deviate significantly from the calculated stationary jump rates, probably because steady state Is not reached fast enough within the time Interval of the relaxation measurements.

Secondly the present relaxation rates from electrical resistivity kinetics under Irradiation are In good accordance for T > 370 K with Zener relaxation rates, which were measured on Identical sample material and Irradiation conditions 111. Below 330 K the agreement becomes poor possibly due to systematic errors of the Zener relaxation strength amplitude determination. The large differen­ces between the present relaxation rates and those from Schule et.a., which both were obtained from electrical resistivity kinetics presumably are caused by a higher residual impurity content of the material which was used in refs. /4/ and /5/.

Ill J. Hillairet, D. Beretz, M. Halbwach8 and E. Balanzat, Conf. on Internal Friction and Ultrasonic Attenuation In Solids, ed. C. C. Smith, Oxford, Fergamon (1980), 143

111 H. Halbwachs, D. Beretz and J. Hillairet, Acta Met. 2]_ (1979) 463 HI C. Abromeit and R. Foerschke, to be published in Rad. Effects /4/ K. Salamon and W. Schule, Rad. Effects 1£ (1972) 45 151 W. Schule and R. Scholz, Rad. Effects JJ1 (1984) 115 161 E. Balanzat and J. Hillalret, J. Phys. F JJ. (1981) 1977

- 59 -

- TIK) 400 350 300

r

10 3/T (K"1)

Fig. 1. Arrhenlus plot of the average relaxation times of the alloy Cu 30 at.X Zn (x) upon thermal treatment Ibl, (•) upon Isothermal electron Irradiation from Zener relaxation kinetics 111, (Ä, ») from resistivity kinetics /4,5/, and (o) from the present work. All data were normalized to the irradiation parameters of Halbwachs et al. 121• The model calculation results are presented by the solid line, the evaluation of the Zener relaxation rates and the rates from the electrical resistivity measurements by Arrhenius laws according to refs. /2,4,5/ by the dashed dotted and dashed lines.

- 60 -

3.6. Dependence of Electrical Resistivity on the Degree of Short Range Clustering in a NiCu Alloy W. Wagner and Ft. Poerschke

The residual electrical resistivity p of alloys varies with the degree of ato­mic order or clustering and is often used as a very sensitive indicator for ato­mic rearrangements. The quantitative interpretation of such resistivity studies is, however, generally handicapped by the fact that the relationship between resistivity and atomic distribution is not known very well. Although a number of theoretical treatments does exist, there was no proper experimental work which would confirm theoretical predictions of more general validity.

In order to close this gap, measurements of the residual electrical resistivity and the diffuse neutron scattering were performed on Ni-41.4 at .3 Cu samples of the same states of short range clustering, achieved by thermal annealing or MeV electron irradiation. Using the Warren-Cowley parameters as derived from the diffuse neutron scattering for various clustering states corresponding to tem­peratures between 380 K and 730 K /l/, the resistivity contribution due to short-range clustering was calculated according to the theoretical formalism of Rossiter and Wells /2/. By comparison with the experimental resistivity data it was shown that, for the investigated alloy and the covered temperature range, the above formalism accounts quantitatively for the dependence of the electrical resistivity on the degree of short-range clustering /3/. This is apparent from fig. 1 where the calculated and measured resistivity data are plotted for their corresponding equilibrium temperature T. It is evident that both sign and magni­tude of the calculated resistivity changes are in excellent agreement with the directly measured data. Moreover, no significant difference occurs between the resistivity changes calculated by using the first shell parameter only or those by using all parameters of the first seven shells. Hence, the main contribution to the resistivity in the present alloy results from the atomic distribution in the first coordination shell. The higher shell contributions were found to be smaller in magnitude and further to compensate each other to some extent.

HI W. Nagner, R. Poerschke, A. Axmann and D. Schwahn , Phys. Rev. B J_l (1980) 3087

IZI P. L. Rossiter and P. Wells, Phil. Mag. 4 (1971) 425 /3/ W. Wagner, R. Poerschke and H. Wollenberger, Phil. Mag. B 43 (1981) 345

- fil -

Kfc [K-1] Flg. 1. Relative resistivity change calculated fron the Warren-Cowley parameters of Hl-Cu (o,x) In coaparlson to the experimental resistivity change data (solid curve). The calculations were done using all parameters for the first seven shells (x), and using only the first shell parameter (o).

- 62 -

o.7. Resistivity Studies of the Short Range Clustering and Long Range Decomposition in Electron Irradiated NiCu Alloys B. Kophamel, ft. Poerschke and W. Wagner

In a Ni-41 at.Z Cu alloy well-defined equilibrium states of short range clustering and corresponding equilibrium resistivity values have been shown to exist abjve T c o n - 525 ± 25 K, the coherent mlsclblllty gap temperature III• For T < T c o n , i.e. within the mlsclblllty gap states of stationary resistivity were determined from resistivity change rate measurements under electron Irra­diation 111. As a result a linear dependence of the thereby determined sta­tionary resistivity on temperature was found over the whole Investigated temperature range 387 K < T < 770 K. To check whether those stationary resis­tivity values represent equilibrium states of the alloy, in the present work long time Irradiations have been applied with fluences up to a factor of 100 higher compared to those in ref. Ill •

In fig. 1 fluence curves of the residual electrical resistivity are shown. Every data point has been measured at 4.2 K after isothermal 3 MeV electron Irradia­tion at the temperatures indicated in the figure. At fluences * > 4.0 • 10^0 cm - 2

the equilibrium resistivity is still not reached, however, the low resistivity change rates Indicate the approach to scationarlty. A raise of the irradiation temperature by 31 K respectively 35 K at this fluence yields first an increase of the resistivity followed by a plateau and finally by a decrease during con­tinuous Irradiation. This behaviour demonstrates that the resistivity changes are not governed by only one relaxation process. Since the irradiation tem­peratures are inside the misclbllity gap, both short range clustering &nd loug range decomposition seem to contribute to the resistivity kinetics, each with a different relaxation time. The longer diffusion paths required for the lung range decomposition may suggest that this accounts for the slower process, while changes in short range clustering require only a few atomic jumps and thus can be significantly faster. Some Indication for the validity of the above assump­tion is gained from the results in fig. 2. There, the plateau values of the resistivity which were obtained after the high fluence irradiation (see fig. 1) and after isothermal postlrradiatlons at different temperatures are shown. A straight line through these data points exhibits a higher slope as compared to the slope of a line through the thermal equilibrium data for temperatures above 640 K. The intersection of the two different resistivity vs. temperature curves coincides well with the Incoherent miscibility gap temperature as determined from neutron scattering experiments /3,4/.

HI R. Poerschke, (J. Thels and H. Wollenberger, J. Phys. F JX) (1980) 67 111 R. Poerschke and H. Wollenberger, J. Phys. F 6 (1976) 27 131 W. Wagner, R. Poerschke, A. Axmann and D. Schwann, Phys. Rev. B 21 (1980)

3087 /4/ W. Wagner, R. Poerschke and H. Wollenberger, J. Phys. F 11^ (1982) 405

- 63 -

35

— 33 E

32

31

30 -

\ i

a 4 0 3 K 0 4 3 4 K * 4 1 5 K 1 « 4 5 0 K -

i

;, -

"A -

- >k -

! 1. . 1

"-

2 3 4 Cb [1020cm-2]

Fig. 1. Resistivity vs. fluence curves of an alloy Nl-41 at.? Cu after isother-•al 3 MeV electron irradiation (d*/dt - 4.2 • 10 1 5 cm - 2 s - 1) at 403 K (A), 415 K (•) for fluences up to 4.3 • 10 2 0 cn~2. For * > 4.3 • 10 2 0 cm - 2 the tem­perature has been changed to 434 K (Q) and 450 K (• ).

" 1 1 ' / •

0 /k 0

f /

' * S« - 5 s ^ ~ O -

1 ,' 7 s /

^ - 1 0 — f / r / S J

- 1 5

i

400 500 600 700 T[K]

Pig. 2. Temperature dependence of the stationary resistivity values deternlned by resistivity change rate measurements 111 ( ) and the resistivity values after high dose irradiations with 2.5 MeV electrons (•) for the alloy Ni-41 at.Z Cu. The symbols • represent equilibrium resistivity values obtained by thermal annealing above T c o h .

- 64 -

3,8. Deviations from Matthießen's Rule in Electron Irradiated NiCu Alloys 6. Kophamel, R. Poerschke and W. Wagner

Theoretical calculations of the electrical resistivity due to changes of the atomic distributions, e.g. short range ordering or clustering, generally refer to the low temperature residual resistivity. In contrast to this, investigations of short range ordering or clustering by electrical resiselvity measurements are very often performed at elevated temperatures. As a consequence the comparison of the experimental results with theoretical calculations requires to separate quantitatively the temperature dependent resistivity contributions from the contributions of the atomic order/disorder. Matthießen's rule p(T) • p(OK) + Ap(T) is an often used tool for this separation, however in many systems devia­tions from Matthießen's rule occur. Such deviations were experimentally deter­mined for the alloys Ni-41.2 at.Z Cu and Ni-53 at.Z Cu. The electrical resisti­vity after thermal treatment and electron irradiation has been measured at 4 K and in addition at elevated temperatures above room temperature. As shown In fig. 1 significant deviations A from Matthießen's rule occur, which possibly indicate positive resistivity contributions due to magnetic scattering. With A from our results the 4 K resistivity can be calculated from on-line resistivity measurements at elevated temperatures-

•(10 1 9 on" 2)

Fig. 1. Fluence dependence of the residual (A) and the 1373 K (U) resistivity changes of the alloy Ni-41 at.Z Cu both normalized to the maximum resistivity change A p 4 K > m a x . 4.085 • 10 - 6 Hem. The quantity A/Ap4 K >„. x, (•) with A , the deviation from Matthießen's rule is also shown.

- 65 -

3.9. Diffusion and Detrapping of Helium and Lithium Implanted in Metals D. Fink, K Tjan and J. R Biersack

laochronal thermal annaaling waa studied up to 1200 C for most of our He and Li implanted samples. Only in few caaea (e.g. B in Si, U in Al, Cu. Nb at low im-plantation doaea) regular thermal diffusion waa obaarved (fig. 1). The majority of all caaaa ia influenced strongly by th« distribution of tha radiation damage. Frequently, a ahift fro» range to damage diatribution is observed during annea­ling,, as tha vacancies may act aa efficient trapa for the Interetitially mobile light impuritiea (e.g. Be in metale). Further, tha annealing behaviour dependa sensitively on th« implanted doae. Finally, for He implants, the thermal He de-aorption is found to occur in definite temperature stepa during isochronal an­nealing, being related to different atomistic mechanisms of He release (fig. 2).

Cu<K.i). 100 KeV ISdOIKKU.AMCM.lMJ 1UMMJTCSI

Z IE-IS

Isochronal annulling ol Ht in PI

m ' nirc • norc

OEFTH IJH1

J00 00 Tl-C)

Fig. 1. Isochronal anneals of Cu(Li), between S00 and 600°C (60 min. each). The diffusion is regular and the profiles agree very well with the computer simulated ones (solid curves). The surface precipitation of the diffused LI is due to their capture as oxld (LijO).

Fig. 2. Isochronal anneals of Pt(He), between 700 and 900*C (1 hour each).

- 66 -

4. MORPHOLOGY AND KINETICS OF THERMALLY ACTIVATED ALLOY DECOMPOSITION __

4.1. Analysis of Carbide Formation in Iron-Chromium Alloys by Field Ion Microscopy R. Lang

The present work Investigates the limitations of FIH with AF analysis of carbide formation In FeCr alloys which are considered to be model alloys for ferrltlc/ martensltlc steels with respect to their behaviour In radiation environments. Carbide evolution under irradiation is one of the Important aspects of the mlcrostructural changes.

Two alloys of compositions A: FeCrl2T10.23CO.23 (In at.X) and B: FeCr8.53T10.42CO.42 have been Investigated. After homogenlntion alloy A was martensltlc and B martensltlc/ferrltlc. After annealing at 823 K carbide partic­les could be Imaged as shown In fig. 1, and the selected area analysis by atom probing of a particle of J n diameter yielded the element contents S3 ± 9 at.Z Ti, 11 * 4 at.Z Cr, 36 ± 5 at.Z C. Hence, the carbide type Is (Tl,Cr)x Cl-x-Particle shapes are spheres, ellipsoids and plates. During annealing the frac­tion of plates decreased from about 201 at the beginning to zero, whereas the fraction of spheres Increased from 5% at the beginning to 50Z after annealing for 600 h.

Grain boundaries could be seen In three sample tips. At the grain boundary the carbide concentration is enhanced and the grains are free of carbides within a 50 tun broad zone along the grain boundary. The average diameter of the grain boundary carbide particles is by about a factor of two larger than those within the grains. Particle size distribution and growth kinetics deviate from the Wagner-Lifshitz-Slyozov predictions /l/.

Ill R. Lang, Diplomarbeit, Technische Universität Berlin, 1984

Fig. 1. FIM Images of carbides (encircled) of different shapes in alloy A after annealing for 40 h at 323 K.

- 67 -

4.2. Atom Probe FIM Study on G. R Zone anay Phase in an Aged Cu-2.1 wt% Be Alloy F. Zhu and R Mertens

The precipitation sequence In a Cu-2.1 wt.Z Be alloy has been studied by many workers using different experimental techniques /1-3/. The decomposition se­quence «ay be described by G.P. zone + Y" + T' * T» The G.P. zones are monolayer plates which for« coherently on { 100) matrix planes. The Y " particles are some­what thicker plates also coherent on { 100J planes. Both structures have often been found difficult to resolve and to Interpret due to the large misfit of pre­cipitates and «atrix and due to the high density of the precipitates.

In this investigation, FIM and atom probe microanalysis were used to study the G.P. zone and Y"-phase in Cu-2.1 wt.Z Be alloy. The material used in this inves­tigation was a Cu-2.1 wt.Z Be alloy. The wire had been solution treated at 800°C for 3 hours, quenched into water, then aged at 300°C for 0.5 or 3 hours to achieve the Tf"-phase or aged at 200°C for periods of 0.5 to 125 hours to achieve G.P. zones. The wires were electropolished to form field ion tips.

A field Ion «lcrograph of the alloy aged 0.5 hour or 3 hours at 300°C is shown in fig. 1. Atom probe selected area analysis revealed that brightly imaged regions are the Cu-rich phase (matrix) and the darkly imaged lamellae are the Be-rlch phase (precipitates). According to computer simulations of field ion laages /5/, three sets of <100> plates should lay in three sets of curved bands foraing angles of 60* with each other in the [ill] centered micrographs. Most of the dark lamellae in fig. 1 coincide with the above scheme. We, therefore, con­clude that they have a habit plane { 100) of the matrix. The edge length of the plates amounts to about 6 - 8 na and the thickness to 1 - 2 nm. Orientation and thickness as well as the heat treatment applied suggests the Identification is Y" /1,2/. The ring structures of the matrix are distorted at the y" precipita­tes, this indicates a relatively large oisflt between matrix and y" precipita­tes. According to Shlaizu's model /6/ the y"-phase may be described as a body-centered tetragonal lattice having a Be-atoa at tl- • body center. The c-axis of the CuAu I(L10) structure Is contracted fro« 3.5f A (lattice constant of the a aatrix) to 2.9 A. A characteristic feature of fig. 1 is the existence of cros­sing dark lamellae, i.e., of the crossing of Y" precipitates. The G.P. zones shown in fig. 2 described in detail more belov also form cross type configura­tions. We believe these crossings to play a kay role for the transition from G.P. zones to Y". The crossings of G.P. zones might be nuclei for the Y"-phase and are obviously regions of the most rapid growth. The latter Is to be concluded fro« the extra width of the dark lamellae near the cross points. A transition of G.P. zones situated at adjacent planes t< a Y"phase /7,8/ cannot be confirmed. Atom probe microanalysis was used to study the composition of the Y"-phase. Fro« analysis of three different precipitates we obtain Cy •• - 50 ± 10 at.% Be in accordance with /6/.

- es -

Ageing at 200°C produces G.P. zones /3/. The field Ion micrographs of this state are shown In Fig. 2. G.P. zones are seen as dark lines oriented parallel to { 100] planes of the Cu-rlch matrix. Many dark lines exhibit irregular widths. This phenomenon can be explained as follows: Employing the model for G.P. zones pro­posed by Gerold /9/, the G.F. zone is a single plane of solute Be between planes of solvent Cu. Our FlM-micrographs indicate that the Be-atoms are more easily evaporated than the Cu-atoms. Thin dark lines in Fig. 2 are interpreted as correct images of the G.P. zones. The thicker ones and also the irregularly shaped ones are interpreted as G.P. images affected by eased evaporation of neighbouring Cu atoms. The growth kinetics of the G.P. zone at 200°C is shown in Fig. 3. The line length was determined by the net plane counting technique. The time exponent for the growth was determined to be 0.14. Some distinctly thicker dark lines were observed in the samples aged at 200°C for longer than 1200 min. Partial formation of y" after long time agein, -annot be excluded.

/I/ R.J. Rioja and D.E. Laughlin, Acta Met. 2J3 (1980) 1301 HI Z. Hermi and T. Nagai, Trans. JIM U> (1969) 166 /3/ V.A. Phillips and L.E. Tanner, Acta Met ?1> 4 4 1 (1973) /4/ P. Mertens, HMI Report 15/ M.K. Miller, S.S. Brenner, M.G. Burke and W.A. Soffa, Scripta Met. 18

(1984) 111 HI K. Shimizu, Y. Mikami, H. MJ---1 and K. Otsuka, Trans JIM 12^ (1971) 206 111 I. Pfeiffer, Z. Metallkde jk_ ,i965) 465 181 S. Yamamoto, M. Matsui and Y. Murakami, Trans JIM JJ2 (1971) 159 191 V. Gerold, Z. Metallkde 45 (1954) 593, 599

- 69 -

Flg. 1 - FIM Image of the Y"-phaae In a Cu-2.1 wt.Z Be alloy aged at 3O0°C for 3 h, [ill] centered. Neon Image, tip temperature about 70 K.

Flg. 2 - FIM Image of G.P. zones In a Cu-2.1 wt.X Be alloy aged at 200°C for 20 h, tip temperature 70 K.

TIME.mins

Fig. 3 - Mean extension of G.P. zones as a functlo*. of ageing time at 200'' .

- 70 -

4.3. Thermal Decomposition in CuNiFe Alloys. Field Ion Microscope and Atom Probe Investigation W. Wagner, J. PillerandRMertens

Whether an observed alloy decomposition is of spinodal type or proceeds by nucleation and growth can only be decided by careful studies of early decompo­sition stages. An alloy system frequently studied with respect to this que­stion is CuNiFe. By reviewing the published results, one may get the Impres­sion that the observation ranges did generally not extend far enough down In order to resolve the truly initial decomposition behaviour. On the other hand, the neutron scattering studies showed the existence of considerable short ran­ge clustering already at high temperatures in this alloy system. Such short range clustered states taken as initial states of decomposition at low tempe­ratures rise the question whether the classical categories of spinodal decom­position and of nucleation and growth might be suitable descriptions of the really undergoing processes.

The present work is part of an attempt to study the decomposition process over wide ranges of the reaction coordinates by applying four different methods: Field Ion Microscopy (FIM), Atom Probing (AP), Neutron Scattering (SANS) and Electron Microscopy (TEM) /1,2,3/. In this article, the FIM and AP results are reported. For the results of SANS and TEM we refer to the following articles (sect. 4.4. and 4.5.). The alloys used for the present investigation are Cu - 46.1 at.% Ni - 4.0 at.% Fe and Cu - 47.8 at.% Ni - 8.0 at.% Fe.

FIM-micrographes of the decomposed alloys (figs. 1 and 2) show under appropiate Imaging conditions bright and dark areas, displaying the two phases in their spatial arrangement. Selected area analysis with the atom probe reveals that the bright imaging phase is enriched in Ni and Fe whereas the dark imaging phase is enriched in Cu. The image shown in fig- 1 shows a regular arrangement of second phase regions, forming a network with <100> orientation correlation to Che ato­mic lattice. The analysis of the microstructure into the depth of the specimens reveals that both phases never form separate Islands but are always constituents of a ramified structure. This is demonstrated by the series of micrographs in fig. 2 showing sections through the specimen, each 2 nm apart from the next one. It can clearly be seen that, as example, the precipitates C, E, F, G appear to be isolated in fig. 2a but are completely linked in fig. 2b and become again separated when going to figs. 2c and d. Sections with isolated brightly imaged precipitates show at the same time linked darkly imaged phase regions. Hence, each phase is manifold Interconnected and both phases intersect each other In a manifold way.

Composition depth profiles for the three alloy constituents obtained by atom probe analysis are shown In fig. 3, for the same decomposition states as pre­sented in the field ion micrograph in fig.l. The graph shows decomposition into Cu- and Ni-rich regions. The Fe is enriched together with Ni. The dash-

- 71 -

dotted linjs give the mean concentration values of the profiles which coincide with the nominal values. The dashed lines Indicate the maximum amplitudes. Not all fluctuations extend to the maximum amplitudes because the enriched or dep­leted regions might not be situated entirely within the probe hole area so that neighbouring regions partly compensate the measured composition fluctua­tion. Kinetics measurements of concentration depth profiles show that In the state presented In flg. 3 the final two-phase compositions are reached. An Increase In compositional amplitude as expected in the case of splnodal decom­position could not be observed above the resolution limit of the AP-analysls which Is reached for second phase regions smaller than about 2 n In diameter.

By means of an autocorrelation analysis the average diameter of the unmixed regions and the wavelength of the modulated structure are obtained. These quan­tities can directly be compared with the corresponding results of the SANS and TEM analaysls. This comparison is given in sect. 4.5., the SANS study.

HI J. Piller, W. Wagner, H. Wollenberger and P. Mertens, 111 W. Wagner, R. Foerschke and H. Wollenberger, 13/ R. P. Wahl and J. Stajer,

all: Int. Conf. on Early Stage Decomposition, Sonnenberg, to be published in Scripta/Acta Met. (1984)

Fig. la) Field Ion micrograph of the 4 at.X Fe alloy after 600 h at 723 K. b) The outline of the features of the observed micrograph depicts clearly the preferred alignment of the fluctuations along the <100)*-direction8.

- 72 ~

Fig. 2. Series of FIM-mlcrographs showing sections through the specimen 2 na apart fron each other. By following certain areas of the image (designed by capital letters) the lnterconnectivity of the mlcrostructure can be observed-

Fig. 3. Concentration profiles of the 4 at.% Fe alloy (same annealing treat­ment as for fig. 1) displayed In phase for the alloying components. The dash-dotted lines stand for the measured concentration average whereas the dashed lines Indicate the maximum deviations of the fluctuations fron the mean avera­ge-

- 73 -

4.4. Thermal Decomposition in CuNiFe Alloys. T E M Investigation RR Wahl and J. Staler

Morphology and kinetics of decomposition in two CuNiFe alloys have been in­vestigated with the help of three experimental techniques namely Transmission Electron Microscopy (TEM), Field Ion Microscopy (FIM) with Atom Probing (AP) and Small Angle Neutron Scattering (SANS) /1,2,3/. This paper reports on the TEM results.

The nominal compositions of the alloys used in this study are: Cu-46.1 at.7.

Nl-4.0 at.Z Fe and Cu-47.8 at.J! Ni - 8.0 a:.Z Fe. Figs, la-c show some typi­cal microstructures developed on ageing the solution treated (1073 K) aud water-quenched alloys. Corresponding selected area diffraction (SAD) patterns, showing satellites to matrix reflections, are also shown. The contrast modulations parallel to the three <100> matrix directions and the satellites, observed on ageing between 673 K and 943 K, suggest the existence of concentration modula­tions along the <100> matrix directions as a result of decomposition of the alloy on ageing. Similar observations have been made by other investigators earlier. The present Investigation shows a dependence of the number of satellite pairs on the Indices (hkl) of the corresponding fundamental reflections. One or more pairs of satellites are absent depending upon whether one or more of the indices (hkl) are zero (figs. la-c). A concentration modulation can cause a modulation in lattice parameter a 0 and/or In atomic scattering factor F. In terms of the existing models on the satellite formation, uhe above observations suggest that their appearance In the present alloys is due to a modulation in a 0.

The kinetics of growth of the contrast modulations is shown in figs. 2 and 3. The wavelength \ of the modulations was determined from micrographs as well as from the position of the satellites l\l. An analysis of the growth kinetics in terms of a power law (Xn - \ 0

n « t) shows that the data can be equally well fitted using different values of n from 3 to 6 and resulting in a new value of X 0 for «ach fit.

Based on an arbitrary pair of reaction parameters (e.g. n, X 0) obtained from data fit, attempts have been made in the past to identify the mechanism of de­composition/growth. Present analysis demonstrates "he need for caution in making such predictions.

I\l R.P. Wahl and J. Stajer 111 J. Plller, W. Wagner, H. Wollenberger and F. Hertens /3/ W. Wagner, R. Poerschke and H. Wollenberger,

all in: Int. Conf. on Early Stage Decomposition of Alloys, Sonnenberg 1983, to be published in Scripta/Acta Het. (1984)

- 74 -

I'll [110] OF with (002)

(a)

B II [112]

(b) Fig.1

BF ? II [1 00] OF with (022)

(C)

• 773 K • 823 Kj. 8 % Fe olloy A 873 K * 723 K 4 % Fe alloy

10 20 3D 40 50 60 210 100 200 300 400 500 600

T.me [ h i

15 -14

• 5 hours

13

1?

• 1 hour i i

_ 10 E

-/ /

8

7

6

/y 693 723 773 823

Temperature IK I

Fig.2 Fig.3

Fig. la-c. Microstructure and satellites in 8 at.X Fe (a,b) and 4 at.Z Fe (c) alloys. a) Aged at 773 K for 8 h, one pair of satellites around (002)m. b) Aged at 823 K for 50 h, three pairs of satellites around (311)m. c) Aged at 723 K for 600 h, two pairs of satellites around (022)m.

Fig. 2. Wavelength X of contrast modulations as a function of the ageing time for different ageing temperatures. The upper time scale corresponds to 8 at.Z Fe alloy and the lover scale to A at.J! Fe alloy.

Fig. 3. Wavelength X of contrast modulations as a function of the ageing tem­peratures for tvo different ageing times-

- 75 -

4.5. Thermal Decomposition in CuNiFe Alloys. Neutron Diffraction Study W. Wagner and Ft. Poerschke

The present Investigation is part of a comparative study of the decomposition

in Cu-Ni-Fe by means of different experimental methods, 1. e. Small Angle

Neutron Scattering (SANS), Field Ion Microscopy (F1M) with Atom Probing (AP)

and Transmission Electron Microscopy (TEM) /1,2,3/. In this article, the SANS

results are reported and discussed In comparison with the parallel FIM, AP and

TEM results.

The specimens for the SANS measurements were so called "null matrices", prepa­

red from material enriched in the Isotop Ni. The alloy compositions were

Cu - 46.1 at.Z 6 2Ni - 4.0 at.2 Fe and Cu - 47.8 at.Z 6 iNi - 8.0 at.% Fe. The

sequences of scattering curves presented in fig. 1 show the kinetics of the

decomposition by means of two exampl • The scattering curves are characterized

by a well-defined maximum at positions of K between 1 and 3 nm"'- (K is the mo­

mentum transfer defined in the usual way by K « 4n A sitß). A maximum of do/dSi,

the differential cross section, Indicates spatially correlated concentration

fluctuations. Two features are evident: the maximum cross section increases and

the position of the maximum shifts to smaller K-values as time passes. In addi­

tion, we observe pronounced cross-overs of the scattering curves for different

times of annealing which as well do shift to lewer K-values with continuing

decomposition. Scattering curves showing such characteristics are predicted by

several theoretical approaches describing an alloy which undergoes decomposition

after quenching from high temperature. Among these are the theories of spinodal

decomposition of e.g. Cahn, Cook or Langer. However, only the nonlinear spinodal

decomposition theory of Langer describes all features including the observed

shifts of the peak position and the shifting cross-overs. As well, the genera­

lized nucleatlon theory of Binder yields results which qualitatively agree with

the observed structure function. The same holds for Monte-Carlo simulations of

the three-dimensional Islng model with nearest neighbour Interactions by Marro,

Bortz, Kalos and Lebowitz.

The maximum position Km(t) and the maximum cross section do/d£l(Km,t) are fre­

quently found to follow the power laws Km(t) « t"a' and do/df) (Km, t) « t

a".

An analysis of the present results in terms of the above given power laws, as

example shown for the peak intensity by the log-log plot in fig. 2, yields..

exponents a' between 0.20 and 0.30 and a" between 0.7 and 0.9. Similar exponents

for peak shift and peak growth are predicted by the nonlinear spinodal decom­

position theory of Langer, the generalized nucleation theory of Binder as well

as by the Ising model calculations of Marro et al. Even the observed slower

onset In peak growth at early times (see fig. 2) Is, for example, explicitly

realized by the numerical calculations of Binder.

- 7fi -

The average wavelengths of the periodic concentration fluctuations, determined from the position of the Intensity maximum, are shown in a log-log plot in fig. 3, In comparison with the FIM and TEM results from alloys of the same com­position /1,3/. By scaling of the experimental times to the temperature depen­dent homologous time t H (623 K) - t e x p • exp(Q/kT) with Q • 2.4 eV the inter-diffusion activation energy from the literature, the study yields the coarsening over 6 orders of magnitude in time and one order of magnitude in wavelength. Over these ranges all data obviously follow a common curve. The temperature independence of XJ^QO a t early times, 1. e. Xioo (t * 0) ~ 2 nm, is probably a consequence of the uniform decomposition path followed during the initial sta­ges, i. e. the evolution of a modulated structure from the quenched short range clustering.

Between 10 7 s and 10 1 1 s the data can be described by a single power law \ n ~ t with n - 4.5 (straight line in fig. 3). We would like to emphasize that during this coarsening process the structure develops starting from a short range clustered state to the highly symmetric ramified structure having a mo­dulation wavelength nearly one order of magnitude larger than the initial sta­tes.

/I/ J. Piller, W. Wagner, H. Kollenberger and P. Mertens, HI W. Wagner, R. Poerschke and H. Wollenberger, /3/ R. P. Wahl and J. Stajer, all in: Int. Conf. on Early Stage Decomposition,

Sonnenberg 1983, to be published in Scripta/Acta Met. (1984) 1 1 1 1 1 1 r-

Fig. 1. Kinetics of the scattering cross section vs. mooentuia transfer of the 4 at.X Fe alloy at different annealing temperatures. Open symbols: T2-measurements (HMI Berlin), filled symbols: Dl1-measurements (ILL Grenoble).

- 77 -

Ti

iHMfc i i illlll|—I I 111 • 11|—I I iiiiii|—I i I Mill)—I l min]—I I 111 ili|—• CuNi«*ot.%Ft T R T K a 171 K »«OK

r CuNUSnt.KFt • 77JK • 723K • Ml K • EDK

y/A

• *—— t « / as I- - jp s

• • " • " | " , | • «••»••j t I I I I J J • t itni.i

<H« Fig. 2. Peak Intensity of the scattering patterns vs. annealing time. The an­nealing tines are scaled to a homologous tine tfj at a temperature of 623 K, accounting for the temperature dependence of the atomic mobility.

SANS *%Fe o 623 K o 673 K

TEM 4V.Fe »723K 8%Fe a773K

SO » 723 K 8% Fe o 623 K

* 681 K

»823K •873K

20 FIM

• 773 K

4 % F e » 723K 8 % F e » 773K y-E10

c \$r 8 •< 5

i i • i

r (-T r

2 4--ry i i

FIM 2 4--ry f

SA

TEM 4--ry f

SA NS 1 * i • • 1 _ i i i

10s K>7 10" 10» 10* 10" tH(623K|(s)

Fig. 3. Log-log plot of the fluctuation wavelengths ver&us homologous annealing time tH, defined as for fig. 2. The AiQQ-values are determined from the SANS peak positions, from AP depth profiles and TEM investigations for both alloys Investigated> f.r various annealing temperatures.

- 78 -

5. MORPHOLOGY AND KINETICS OF ALLOY DECOMPOSITION UNDER IRRADIATION

5.1. The Influence of Cascade Effects on the Stability of Precipitates C. Abromeit and V. Naundorf

In the last few years many attempts were made to describe the stability of al­loys under Irradiation theoretically. Different mechanisms and their influence on the shrinkage or growth of precipitates are discussed. Here the nodal line/ critical point formalism Is extended In order to include cascade effects caused by Ion bombardments or neutron irradiation. The combination of two atomistic models leads to a modified description of phase stability under Irradiation III.

We consider the evolution of pure solute precipitates in a solvent matrix. A precipitate is described in the same manner as given by K. C. Russell 121. The characteristic parameters of a precipitate are the number of solute atoms x and the number of "excess" vacancies n. A spherical surface is assumed. The environ­ment of the precipitate Is also of spherical symmetry.

The kinetic evolution of the precipitate and its stability is determined by the fluxes of solutes, vacancies and self-lnterstitlals towards the precipitate sur­face or away from it. Hence the kinetics can be written in the form of balance equations for the changes in x and n. The time evolution of (n, x)-precipitates is therefore represent?'] by trajectories in an (n, x) plane. They are determined by the capture rates and emission rates for solute atoms, vacancies and self-interstitials.

Simple models for the capture rates B are treated which nevertheless give the essential results for solute precipitate stability under Irradiation. One ba­sic assumption Is that the diffusing species are captured when reaching the Burface of the precipitate. All locally dependent terms are neglected, so that the capture rate for this process only depends on the radius of the precipita­te. Another capture process without diffusion should be discussed for ion or East neutron irradiations. If a collision cascade occurs just in the neighbour­hood of a precipitate, interstitial solvent atoms produced by this cascade can be shot towards the precipitate. This process gives a capture rate for lnterstltlals, which Is proportional to the surface of the precipitate.

Two different models of dissolution of precipitates under Irradiation are dis­cussed. One was proposed by K. C. Russell 111 and considers new thermodynamic equilibrium conditions under irradiation because of the enhanced defect con­centrations. The dissolution rates are given in terms of the Glbbs free energy for forming a precipitate In the absence of self-lnterstitials. The other model of dissolution has been proposed by R. S. Nelson /3/ and discusses processes which «ra present only for Ion or neutron irradiation. They are based on the direct interaction of the cascades with the precipitate. The precipitated solute atoms are displaced either by a recoil process at the surface like surface sput­tering or by order - disorder transformations.

- 70 -

The solution of the resulting kinetic equations can be constructed by a proce­dure as given by K. C. Russell /2/. The (x, n) plane la divided Into two parts by nodal lines x « o (n • o), «here the sign of the time derivative changes. The kinetic evolution of an (n, x)-prccipltate can be constructed by superposition of the two nodal lines x • o and n - o. The results are shown in figs, la.b.c for positive voluae misfit of the solute and vacancy superiaturatlon qualita­tively.

Fig. la gives the evolution of a supersaturated solution without Irradiation. Any (n, x) precipitate develops into the regions within the two nodal lines. Then it will either grow or shrink according to whether x is larger or smaller than a critical value, x c r i f

The Influence of an irradiation with small cascade effect can be seen in fig. lb. The critical size x,.rit decreases but for large x there is a second inter­section point x at a|,i c of the nodal lines. This point corresponds to the equi­librium radius of the precipitate without vacancy effects according to /3/. Three different regions are to be distinguished: (i) x K x c rit dissolution, (ii) x e rie < x < xatible growth and (ill) x < Xgtable shrinkage of the precipi­tates after It has developed Into the section between the nodal lines. For strong cascade Influence x c rit ^ ^stable. I n this case, there is no intersection point (fig. lc). Therefore any (n, x) precipitate will dissolve completely. The exact values of *crit and xstable depend on the models used for the capture and emission rates.

HI C. Abromeit, Proc. Int. Conf. on Irradiation Behaviour of Metallic Materials for Fast Reactor Core Components, Ajacclo (1979) 89.

III S.I. Maydet and K.C. Russell, J. tfucl. Mater. 6± (1977) 101. IV R.S. Nelson, J.A. Hudson and D.J. Mazey, J. Nucl. Mater. 44 (-972) 318.

- 80 -

Flg. 1. Diagrams show the direction of motion of a precipitate particle a) without irradiation, b) with small cascade Influence, c) with strong cascade Influence.

- 81 -

5.2. Radiation Induced instability and its Influence on the Decomposition of a Concentrated Alloy C. Aoromeit and K. Krishan (RRC Kalpakkam, India)

Several concentrated alloys are known to show splnodal decomposition. The theoretical models are based on equilibrium thermodynamics (e.g. Cahn /I/ and Cook 121). However, In some of these concentrated alloys the thermodynamic decomposition is predicted in a temperature range where the atomic mobility is too small and the phase separation Is not observed for reasonably long experi­mental times under thermal conditions, whereas long-range concentration fluc­tuations develop under electron irradiation (see sect. 5.4). An Important question which arises concerns the role of the electron irradiation. Two points of view can be considered, (1) the -ole of the irradiation is only to enhance the diffusion but the decomposition is still governed by the thermodynamic pro­cesses, (11) the long-range periodic decomposition is induced by the irradiation Itself. To distinguish between these two physical mechanisms one has to examine the kinetics of the decomposition in detail. It is therefore useful to examine whether In such a concentrated alloy an irradiation-induced metastablllty can develop which could drive the long-range composition fluctuations. He have deve­loped such a model and have discussed the physical mechanisms which can cause the instability /3/.

The &y*tem is treated as a dissipative structure in whl . a small bias in the vacancy-interstitial recombination reaction and irradiation mixi-.g effects in zones of concentration fluctuations produces fluxes of Interstitials leading to growth and shrinkage of such zones. The system is modelled in a mean-field treatment as a homogeneous lossy medium with a non-linear coupling of the defect concentrations and an averaged parameter characterising these zones.

Following the notation of /3/, P^ 1 and P B 1 are the A and B interstitial produc­tion rates whose dynamic concentrations are I A and Ig. V is the concentration of vacancies. The time development of these concentrations is given by

77 X A - P A 1 - RA IA V + D A V 2 I A " (i) at

— lJI" rJ? - KB *A V + DB 7 2 l B (2) dt i- V - P 0 - (K A-I A + K B-I B)V + Dv ' 2 V (3) d t

where P 0 is the sum of P AV a n (i p BV ti, e production rate for vacancies at A and B atom lattice sites. The small bias in the recombination rate is modelled by the equations (£ A the local concentration of A . \ttice atc-s)

*A,a ' KA,B(£A> " KA,U°(*A> + »A,B«A " XA> (*)

- 82 -

where XA is the average concentration of the alloy defined by XA - 1/Ö/?A d x

and !) Is the integration volume. The interstitial production rates depend on ? A

and also on the amount of mixing m caused by the Irradiation,

PA.B 1 " Po <*A,B " (• -1)(5A,B " *A,ß) > (5>

From these equations we have defined the decomposition parameter n " 5 A ~ XA which is easily related with the structure factor used in the thermodynamic theories S(k_,t).The time dependence for n Is given by

V V 7- n - - « B PA - C A PB> + « B K A IA - 5 A KB IB) V (6) dt

which gives the balance of the loss by the production of interstitials and the gain by recombination. Equations (1) - (6) define the differential equation system which describes the kinetics of the decomposition. The dependence of the production rate and recombination on the local variables 5A o r n makes the equa­tions nonlinear.

Main features of these equations are extracted by using a linear stability ana­lysis. Following the well established procedure /4/ we attempted a spatial and temporal solution for the deviations from the homogeneous steady state in the form exp{ ik'r + <ii (k)t}. The solution ID (k) gives the dispersion relations of the system, and plays the same role as the amplification factor a in thermo­dynamic theories of spinodal decomposition. In our present analysis we have con­sidered a linear superposition of the amplification factors to obtain an effective amplification factor a eff - a + u ',%?)• One of the effects of the irradiation will be to shift the cross ji-er point k » k c where the amplification factor a(k c) 1E zero in the Cahn-Cook moc jl /1-2/ according to

k zc - k 2

c(thermal) + Dmi x/ Mirr K (7)

with Dmlx the radiation induced mixing diffusion coefficient, H^ r r the radia­tion enhanced diffusion coefficient and K the gradient energy term. The linear stability analysis also shows that an Instability can develop in such a solid solution leading to periodic concentration fluctuations. The model yields a tem­perature- and dose-independent wavelength.

/I/ J. W. i.ann, Acta Met. 9 (19H1) 795 III H. E. Cook, Acta Met. \%_ (1970) 297 IV K. Krishan and C. Abromelt, J. Phys. F J^ (1984) 1103. / V G. Nlcolis and I. Prigoglne. Self-Organization in Nonequilibrium

Systems (New York : Wiley)

- S3

5.3. Radiation-Induced Segregation in NiCu Alloys W. Wagner, V. Naundorf, L £ Rehn * and H. Wiedersich (*ANLArgonne,USA)

Radiation induced segregation (RIS) has its origin in the coupling between de­fect fluxes and fluxes of alloying elenents, which produces concentration gra­dients of these elements In the vicinity of defect sinks like dislocations, grain boundaries and, in particular, the external surface. In the near-surface region, the one dimensional concentration gradients Induced by RIS can be mea­sured with surface sensitive analytical methods like Auger Electron Spectroscopy (AES) in combination with ion sputtering, or Rutherford Backscattering Spectro­metry (RBS).

Both methods were applied for a detailed and systematic experimental study of RIS in two concentrated alloys of the NiCu-system, Ni-10at.Z Cu and Ni-60at.Z Cu/1,2/. The system NICu was chosen because it exhibits complete miscibility for temperatures above 300*C in contrast to other systems where a pronounced RIS effect has been determined, e. g. Cu(Be) and Ni(Si). RIS In concentrated Ni-Cu alloys, therefore, can be investigated without the added complication of phase separation.

The surface segregation for different doses ranging from 0.2 to 5 dpa and tempe­ratures between 420*C and 610*C in both alloys was studied by AES depth-profiling after 3 HeV Ni + (self-ion) irradiation, supplemented by "in situ" RBS measure­ments during 2 HeV He+-ion bombardment. Both methods reveal a strong segregation of Ni to the external surface (figs. 1 and 2). The Ni enrichment at the surface is accompanied by a Cu-enrichsd (Ni-depleted) region at intermediate depths (see fig.l). The width of the segregated region increases with increasing dose and irradiation temperature, extending up to ~ 170 no after 5 dpa at 610°C.

The radiation induced nature of the segregation was demonstrated by a post-irradiation annealing experiment: The segregation disappears when the specimen after irradiation is annealed at the irradiation temperature, showing that the segregation is thermally unstable and therefore induced by the irradiation.

The experimentally determined concentration depth profiles were quantitatively evaluated by theoretical calculations, using the model of RIS in concentrated alloys developed by Wiedersich, Okamoto and Lam /3/. The model allows for pre­ferential migration of point defects (vacancies and interstitials) via Ni-atoms or Cu-atoms, permitting the defect fluxes and the atom fluxes to be exp­ressed In terms of partial diffusion coefficients. It must be emphasized that all measured concentration depth profiles were satisfactorily reproduced by the model calculations with a single set of input parameters for each alloy• Some of these parameters, results of a procedure which fits the theoretical calculations to the data, are listed in Tab. I. They contain valuable informa­tion on defect-solute interactions in the concentrated alloys which normally

- 84 -

are not assessible in such detail. For example, the migration enthalpies of A(Cu)- or B(Nl)-atoms via vacancies and interstitials mainly determine the par­tial mobilities of the atoms via the different defect species, as well as a pre­ferential association between the defects and the different atomic constituents.

The derived values Indicate that In the 10 at.7. Cu alloy, the model requires both preferential transport of nickel atoms toward the surface via the inter­stitial flux and preferential transport of copper atoms into the bulk via the vacancy flux to reproduce the measured concentration profiles. In the 60 at.Z Cu alloy, the model explains the results equally well with preferential tran­sport of nickel atoms by interstitlals, preferential transport of copper atoms via vacancies, or by a combination of these two transport mechanisms.

I\l W. Wagner, V. Naundorf, L. E. Renn and H. Wledersich, Effects of Radiation on Materials: Eleventh Conference, ASTM STP 782, edited by H. R. Brager and J. S. Ferrin (American Society for Testing and Materials, Philadelphia, 1982) 895

/2/ W. Wagner, L. E. Rehn, H. Wiederslch and V. Naundorf, Phys. Rev. B 28, (1983) 6780

/3/ H. Wiederslch, P. R. Okamoto and N. Q. Lam, J. Nucl. Mater. 83 (1979) 98

1000

SPUTTERIHC TIME IS) 1000 1500

SPUTTERINC TWC IS]

Fig. 1. AES depth profiles of the Cu concentration for Ni - 10 at.Z Cu and Ni - 60 at.Z Cu, Irradiated with 3 MeV Ni + ions at different temperatures, along with the depth profiles of unirradiated control specimens.

- «5 -

^ • A y ^ v ^ V s ^ i

2INVHT I I I KT4 <M/I SM'C

300 390 400 omnia Nune«

400

CHdHNEL MJUBER

Fig. 2 a) BBS spectra acquired during Irradiation of a Ni - 60 at.! Cu alloy at 535'C with 2 MeV Be+ Ions.

Fig. 2 b) RBS yield differences, obtained from the spectra by subtracting the yields of the first 5 nlnutea of acquisition. Solid lines are yield differen­ces obtained by computer slnulatlon with composition depth profiles like those of Fig. 1.

Parameter 10 a t . « Cu 60at.% Cu

Migration enthalpies (eV)

Sink density Recombination ndius Defect production efficiency

HA. H» KM Km c.

P

1.00 1.15 0.30 0.12 sio- 1

O.Soo 0.40

1.06 1.12 0.20 0.20

1.06 1.06 0.23 0.17

sio-' 0.8a, 0.40

Tab. 1: Derived parameters for the beat fit of the RIS model to the experimental data, k means Cu and I SI, v vacancies and 1 interstltials. For the 10 at.* Cu alloy, both parameter columns equally well describe the experimental data.

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5.4. Short-Range Clustering and Long-Range Periodic Decomposition of an Electron Irradiated NiCu Alloy W. Wagner and Ft. Poerschke

NiCu Is one of the few alloy systems which show complete miscibllity in the solid state. However, its tendency to short range clustering (SRC) strongly suggested the presence of a miscibility gap at temperatures below 600 K. In this temperature range thermally activated mass transport is too small for an experi­mental verification. Only irradiation enhanced diffusion can provide sufficient atomic mobili'.y, due to the migration of irradiation induced point defects. It was found that such point defects do cause an effective mass transport in NiCu alloys, even at temperatures as low as 100 K /l/. Refering to these experiments, we investigated the alloy Nl- 41.4 at.Z Cu after thermal annealing at tempera­tures between 600 K and 973 K an-J after irradiation with 3 MeV electrons at tem­peratures between 373 K and 600 K 111- The applied experimental methods were electrical resistivity measurements, Diffuse Neutron Scattering (DNS) and Small Angle Neutron Scattering (SANS). The specimens designed for the neutron diffrac­tion measurements were prepared from material enriched in the isotopes 6 2Ni and •>5cu. Due to the negative scattering length of ^fli the order disorder scat­tering contributions are drastically amplified while the fundamental scattering contributions in the present alloy are completely absent ('null matrix').

Examples of the diffuse SRC scattering of the 'null matrix' are shown in fig. 1. The equilibrium states of short range clustering above 600 K were analysed in terms of the Ornstein Zernicke theory. This analysis yielded the temperature

2 dependent quantities, f"+2n Y, the second derivative of the free energy with respect to the concentration plus the elastic energy, and K, the gradient energy coefficient. From a linear extrapolation of these thermodynamical data the cohe­rent mlscibillty gap temperature Tcof, - 527 t 25 K was obtained. Furthermore from fits of the SRC scattering contribution to the DNS data (solid curves in fig. 1), the Warren-Cowley parameters for the first seven atomic shells were determined for different states of thermal treatment and irradiation. From the kinetics of the Warren-Cowley parameters relaxation rates and interdiffusion coefficients have been derived which are in good accordance to rate equation calculations of the defect concentrations upon irradiation. As well, comparable interdiffusion coefficients were obtained from fits of the linear splnodal decomposition model of Cook, Hilliard and de Fontaine to the short range clustering part of the diffuse scattering curves using thermcaynamical parame-

2 ters f"+2n 1 and K extrapolated from T >" T c o n to the irradiation temperatures at T < T c o h IV.

Besides the short range clustering contributions in the scattering curves, a pronounced intensity maximum in the small angle range occured after electron irradiation at temperatures between 373 K and 480 K (fig. 2). This intensity maximum is originated by a periodic long range decomposition, giving the first experimental evidence of the suggested miscibility gap in NiCu. From the maximum

- 87 -

position, a fluctuation wavelength around 4.5 na was derived. The decomposition structure was found to be stable against thermal annealing and irradiation, at least up to S10 X. Upon thermal treatment above 600 K the long-range decom­position dissolves.

The decomposition kinetics for T < Teot, can be described satisfactorily by Cook's clustering model for large scattering wavevectorB, i.e. for the short-range clustering. However, the small-angle peak kinetics show several specific deviations from the predictions of the common splnodal decomposition theories. The possibility cannot be excluded that the observed long-range decomposition is an Irradiation-induced phase transformation. In this case the decomposition of the system according to equilibrium thermodynamics could exhibit different characteristics•

HI R. Poerschke and H. Wollenberger, J. Phys. F 6_ (1976) 27 111 W. Wagner, R. Poerschke, A. Axmann and D. Schwann, Phys. Rev. B 2_1 (1980)

3087 /3/ W. Wsgner, R. Poerschke an<< H. Wollenberger, J. Phys. F _ 2 (1982) 405

Fig. 1. Typical diffuse SRC-scattering patterns of the "null matrix" after thermal treatment and after irradiation, measured at the multidetector diffrac-tometer at BER II. The fit of the theoretical SRC scattering contributions to the experimental data (solid curves) yields the Warren-Cowley parameters for the first seven shells.

- 88 -

I 1 1 1 — i I 1 I I . 1 L-0 OS 1 15 0 OS 1 15 0 (15 1 15

Fig. 2- Scattering curves of the null matrix In the small angle range, after the preparatory thermal treatment (6 h at 870 K) and after subsequent electron Irra­diation* The intensity maximum indicates long-range periodic composition fluc­tuations, the first experimental evidence for a misclbility gap In NiCu.

- 89 -

5.5. Electron Irradiation as a Tool for Alloy Decomposition Studies at Low Temperatures: Neutron Scattering on Electron Irradiated NrCu Alloys Ft. Poerschke andD. Schwahn (KFA Jülich)

To study the Influence of the thermal treatment In the homophase region of the phase diagram on the decomposition under electron Irradiation at temperatures below Tcohf C n * coherent miscibility gap temperature, SANS and DNS measurements haye been performed on the "null-matrix" Ni-41 at.2 Cu. The scattering cur­ves as obtained after slow furnace cooling from 873 K and after quenching from 1073 K and the 423 K kinetics under electron irradiation are shown in fig. 1. Obviously significant difference) occur between the decomposition kinetics un­der irradiation f'tr different thermal pretreatments. In the slowly cooled sample negative cross section changes and the build-up of pronounced maxima for < = 0.17 A - 1 Indicate a rearrangement of the clusters due to the thermal pretreat-ment Into a periodic atructure with a characteristic wavelength of around 30 A /1,2/. In contrast to this, starting from a small degree of short range clustering as obtained by quenching from 1073 K, merely positive cross section changes and continuously shifting cross section maxima were observed as pre­dicted from the more elaborate theories of spinodal decomposition. The theory of Cook, Hllliard and de Fontaine (CHF) 13/ which is a linear model and can thus be treated analytically has been fitted to our data with the result given in fig. 2 /A/. Excellent accordance between theory and the scattering curves has been obtained with reasonable parameter values for Dchem> t h e chemical diffusion

coefficient and K, the gradient energy coefficient. Positive values of the c-.-m-2

tity f"+2n Y, the second derivative of the free energy with respect to the con­centration plus elastic energy term, were derived from the fit, whereas negative values would be expected for T < Tcoh" Positive f"+2n Y have also been found in electron Irradiated Cuo,5()Nio.48Fe0.02 al^°5's a n d l n thermally annealed C u0.48 N i0.48 F e0.04 «Hoys in the very early stages of the decomposition /5,6/. Hence, possibly this Indicates that the extrapolation of the thermodynamical

2 parameter f"+2n Y from the single phase region into the two phase region cannot be done straight forward with the random solid solution model as suggested in ref. 111.

Ill W. Wagner, R. Poerschke, A. Axmann and D. Schwahn, Phys. Rev. B21 (1980) 3087 111 W. Wagner, R. Poerschke and H. Wollenberger, J. Phys. F 12_ (1982) 405 131 H.E. Cook, Acta Met. Jj! (1970) 297 IUI R. Poerschke and D. Schwahn, Froc. Int. Conf. on Early Stage Decomposition,

Sonnenberg, to be published in Scripta/Acta Met. 151 H.W. GHlllng, R. Poerschke, D. Schwahn and H. Wollenberger, Proc. Int.

Conf. on Phase Transformations in Solids, Ed. Thomas Tsakalakos, Crete 1982, North Holland Publ.

161 W. Wagner, R. Foerschke and H. Wollenberger, as in M/

- 90 -

Flg. 1. Fluence dependence of the DNS and SANS pattern for 2 HeV electron Irradiation at 423 K with fluences of * (1019 cm - 2): o - 0, x - 4.22, • - 10.17 and A - 16.83. The 423 K irradiation data subsequent to furnace cooling from 873 K ( ) according to Wagner et. al /3/ are also shown (t (lO^' cm - 2): (—) - 0.66 and ( ) - 1.84).

1 -i

(b)

1 0 0.5 x |A-'I

0 1 0

Fig. 2. Comparison of the data from fig. 1 with model calculations according to the CHF theory (solid lines) (* (1019 c m - 2 ) : a - 4.22, b - 10.17 and c - 16.83). For the highest fluence also a calculation for t + <• has been Included (dashed line).

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5.6. Neutron Scattering Studies of the Short Range Clustering and the Long Range Decomposition in CuNiFe Alloys R. Poerschke, H. W. Galling and Ü. Schwann (KFA Jülich)

Upon Ffc addition to CuNi alloys the mlscibility gap temperature is raised si­gnificantly. Fro» SANS and DNS measurements on null-matrices of alloys

2 CuNio.4gFeo,oo5 and CuNio.4gFeQ.02 the thermodynamical parameters f"+2n Y and 2 2

K C - (f"+2ri Y)/2 K have been determined according to an Ornstein-Zernicke an­alysis, f" is the second derivative of the free energy with respect to the

2 concentration, 2n Y an elastic energy term composed of n - (l/a)(da/dc), the relative lattice parameter change with respect to concentration and Y the elastic modulus averaged over the different lattice directions, K is the gra­dient energy coefficient. From the temperature dependent parameters (fig. 1) the coherent mlsclbllity gap temperatures T c o n were determined (see fig. 1). The Fe additions lead to significantly higher T c o n as compared to the pure CuNi alloy. Furthermore with increasing Fe content the gradient energy coeffi­cient Increases significantly.

Upon HeV electron irradiation at temperatures T < Tcoh typically a sequence of 1 9 scattering curves as shown in fig. 2 is observed. For fluences * < 5 x 10

cm - 2 a common tail of the scattering curves for < > < m - with <m, the position of the maximum cross section exists. Therefore the curves have been evaluated with the Cook-Hilliard-de Fontaine model /1-3/. One example of the excellent accordance between the theory and the experimental data Is shown in fig. 3. The temperature dependent chemical diffusion coefficient n

c n e n a s derived

from fits of model calculations to the data is shown in fig. A. The order of magnitude and the activation energy of Dchea (**8* 4a) are in reasonable ac­cordance to the results of rate equation calculations with defect migration energies and defect production rates from the literature. The gradient energy coefficients K from the model calculations are also In reasonable accordance to K as derived from homophase equilibrium states (fig. Ab). The quantity

2 f"+2n Y shows values around zero instead of negative ones which would be ex­pected from a linear extrapolation of the homophase values to temperatures vl-2 thin the miscibility gap (fig. 4c). Since positive f"+2n Y values occur also for the early stages of thermal decomposition of an alloy CuNio.4gFeQ.04 they give no evidence for an irradiation Influence on the decomposition kinetics besides the radiation enhanced diffusion.

K comparison of the decomposition kinetics of the 2 at.J Fe alloy under irra­diation with the thermal kinetics of a A at-Z Fe alloy according to /A/ is shown In a log-log plot of the maximum cross sections (do/dS))m and their positions < m

versus annealing times, respectively irradiation times (fig. 5). Obviously the kinetics of both quantities for A73 K electron irradiation and 623 K thermal annealing look very similar. Thus, neglecting the different alloy compositions from this comparison the power of the irradiation to save a factor of about 106

in time for the investigation of the decomposition kinetics without changing the thermodynamics of the system significantly seems to be clearly demonstrated.

- 92 -

Ill H.E. Cook, D. de Fontaine and J.E. Hllllard, Acta Metall. L7 (1969) 765 111 H.E. Cook, J. Phys. Chem. Solids j|0 (1969) 2427 131 H.E. Cook, Acta Metall. 8 (1970) 297 /A/ W. Wagner, R. Poerschke and H. Wollenberger, Int. Conf. on Early Stage

Decomposition In Alloys, Sonnenberg 1983, to be published In Scrlpta/Acta Metall. (1984)

151 W. Wagner, R. Poerschke and H. Wollenberger, J. Fhys. F 12. <1982) 405

Fig. 1. Thermodynamlcal parameters from DNS and SANS measurements the mlsclbl-llty gap as a function of the temperature for different Fe content. The data of the pure CuNl alloy according to Wagner et al. 151 are also shown.

Fig. 2. SANS kinetics of the alloy CUQ.jo N 10.48 F e0.02 ""der 2 MeV electron irradiation at 473 K (d*/dt - 7.1 x 10 1 3 en - 2 s - 1) for * (10 1 9 c m - 2 ) : o - 0.5, - 1.11, - 2.54, x - 5.0, • - 9.14 and A - 20.7. The initial state (+) has been achieved by means of quenching from 973 K after 2 h annealing.

1- 3 o

c

° 7

•oho

1

0 0 05 1 15

Fig. 3. Fit of the CHF model to the cross section obtained after isothermal 2 MeV electron Irradiation with * - 6.3 x 10 1' cm"2 at 423 K.

- o-? -

' • • / ' / / / J / / /

. • /

d--+- / / / . lO'/T (X°J

Fig. 4a. Arrhenlus diagram of the chemical diffusion coefficient as derived from fits of the CHF-model to the SANS data of a Cuo.5oNio.48Fe0.02 a l l o v u n " der 2 MeV electron Irradiation (d*/dt - 1.8 x 1014 cm - 2 s - 1 ) .

Fig. 4b and c. Temperature dependence of the gradient energy coefficient (b) 2 and the free and elastic energy term f"+2n Y (c).

Fig. 5. Kinetics of the SANS cross section maxima do/dn(icm) and the correspond­ing momentum transfer Ka under thermal annealing of a 4 at. J Fe containing alloy at 623 K (x,C ) and 673 K (o,A) and under 2 MeV electron irradiation of a 2 ac.% Fe containing alloy at 473 K (•,»).

- 94 -

5.7. Formation of Dislocation Loops in CuNi under 300 keV C u + Ion Irradiation P. Dauben and Ft. P Wahi

The intrinsic point defects created by displacement events during irradiation frequently cluster to form vacancy or interstitial dislocation loops. The beha­viour of such aggregates during subsequent irradiation is of considerable impor­tance to our understanding of the overall evolving microstructure in materials.

In this paper the results on the dislocation loop formation in CuNi alloys under 300 keV ion irradiation are presented. Experimental conditions: Specimens of pure copper and CuNi alloys with 1 to 58.6 at.2 Ni were irradiated at 700 K vdth 300 keV Cu+-ions in the displacement rate range of 3- 10"* dpa/sec-7- 10~3 dpa/sec The total fluence varied from 0.2 dpa to 14.7 dpa.

After irradiation the dislocation loops were uniformly distributed and grouped into two distinct size classes - large loops of mean diameter d - 13 nm having a point density of = 5* 10^ cm--* and smaller loops (d < 4 nm) having a point density one order of magnitude higher. The latter appeared as black/white con­trast and were identified as perfect loops (b » .1 • -4ll0>), whereas the larger loops were identified as ~ 70% Frank loops (b « a/3 <111>) and ~ 30% perfect loops.

By applying the 2 1/2-D-method /l/ the small loops could be analysed as vacancy loops. The determination of the vacancy/Interstitial nature of the larger loops was not possible, because the ± g-method of analysis 121 requires imaging of the Kikuchi diagram which could not be achieved in the Irradiated specimens. But on the basis of growth kinetics calculations for dislocation loops under the pre­sent Irradiation conditions /3/f interstitial nature was concluded for the large loops. All measured parameters like loop density, diameter, Burgers vector and loop nature did not change, within the experimental uncertainty, with the irra­diation conditions.

These results show that the density and size of the loops saturate very early In the course of irradiation so that within the range of fluence employed in the present investigation these parameters remain approximately constant. This beha­viour can be qualitatively understood in terms of the proposed growth mechanisms for dislocation loops under Irradiation /3,4/.

/I/ J.B. Mitchell and W.L. Bell, Acta Met. 2_4 (1976) 147 111 J.W. Edington, Interpretation of Transmission Elect on Micrographs 3,

N.V. Philips, Gloeilampenfabrieken, Eindhoven, (1975) 111 A.J.E. Foreman and M.J. Makin, J. Nucl. Mater. _7£ (1979) 43 /4/ A.D. Brailsford, J. Nucl. Mater. Sji (1979) 269

- 95 -

5.8. Morphology and Kinetics of Microstructural Evolution in a CuBe Alloy under 300 keV Cu + Ion Irradiation R.Koch and RPWahi

Introduction

The CuBe alloys represent an Interesting alloy system for studying radiation Induced phase changes because of the large volume misfit (-26Z) caused by Be atoms In Cu lattice. Earlier experiments on dilute CuBe alloys involving elec­trical resistivity measurements after electron irradiation have shown that the Be concentration in the matrix decreases linearly with the irradiation dose III. Diffusion study on a dilute CuBe alloy under irradiation has revealed fast dif­fusion of Be even at room temperature 111• This paper reports the results of an Investigation 131 to study the morphology and kinetics of microstructural evolu­tion in a Cu-1.35 at.I Be alloy subjected to 300 keV Cu + ion Irradiation. This alloy is undersaturated above 570 E. Studies of thermal decomposition on ageing of supersaturated CuBe alloys reported in literature have shown the formation of an ordered (B2) phase Y (a0- 0.269 nm) as the stable phase. This phase precipi­tates either directly from the matrix forming on dislocations/grain boundaries or homogeneously via a sequence of metastable phases including G.P. zones.

Results

1. Irradiation at temperatures between 500 and 670 K produced fine precipita­tes of the Y phase (fig. 1) and very small dislocation loops identified as F*ank loops (b » a/3[lll]) of vacancy type. Volume density py of both was around lOl« cm'-* at and below 600 K and fell to smaller values at higher tem­peratures.

2. Reheating the irradiated specimens to temperatures between 600 and 680 K caused the precipitates to dissolve.

3. No precipitation was detected In specimens irradiated below 500 K.

4. The precipitates grow with fluence to a stationary diameter d» which shows a weak dependence on the defect production rate KQ (figs. 2a-c) and a strong dependence on T (figs. 3a,b).

Discussion

The observed formation of Y precipitates under irradiation and their »disso­lution on thermal annealing confirm that the precipitation is radiation indu­ced. We interpret this phenomenon in terms of existing models for solute se­gregation on point defect sinks caused by radiation Induced flux of point de­fects to the sinks /1,4/. The following discussion of the present data on the growth kinetics of Y precipitates is based on this Interpretation of precipi­tate nucleation:

- 96 -

The evolution of the precipitates to a stationary diameter (figs. 2a-c) has been Interpreted /3/ as a result of a dynamic equilibrium between radiation Induced growth and acheroal dissolution through collision cascades. Using the simple expression for growth In the presence of a solute concentration gradient around the precipitates and taking the athermal cascade dissolution of the small preci­pitates to be proportional to their volume, the total growth rate of the average precipitate volume ~V can be written as:

V - ^ r r B e - Kr-V (1)

Here d: Average diameter of the precipitates nlrr : Effective diffusion coefficient under radiation Cj)e(pv,R): Average concentration of Be in the matrix C„ : Concentration of Be in a precipitate (" 0.5) K r : Rate constant for cascade dissolution

The curves shown In figs. 2a-c are obtained by numerical integration of the above expression and fitting the resultant data to the measured growth data. This procedure yields two important parameters K r and D i r r . it is found that K r - KQ for all irradiation conditions. The derived valaes of D j r r as a func­tion of KQ at 600 K are shown in fig. 4a. The value of !.0_1* cm2 * s"1 at K 0 - 5 * 10~3 dpa * s - 1 is in reasonable agreement with the value of 2 * 1 0 - 1 5

cm2 * s~l at Kg • 4.5 * 10"^ dpa * s -* measured under similar Irradiation conditions by means of SIMS 111. Also shown In fig. 4a is the dependence of D l r r on Kg calculated according to reference 15/ for different modes of point defect annihilation namely a) through recombination (D^ r r« K ^ / 2 ) , b) at sinks (D l r r» Ko) and c) In the transition case involving both recombination and anni­hilation at sinks 16/. The behaviours a) and b) are represented by solid lines, whereas c) by the dashed curve. The data in fig. 4a show that the measured dependence of n i r c on Kg can be understood in terns of a transition behaviour of point defect annihilation. An estimate of the point defect sink strength (which is proportional to the volume density of the sinks) from the fit in fig. 4a yields a minimum sink strength of 3 * 10 l x cm2. This figure agrees well with 4 * 10*1 cm2 derived from the diffusion coefficient measurements by SIMS 111.

The observed volume density py of y precipitates and dislocation loops of around 101* cm~3 however corresponds to an average sink strength of about 3 * 10 1 0 cm"2. We conclude that the self Ion irradiation produces predominant­ly point defect sinks which are not resolved by the normal TEM technique.

- qj -

The temperature dependence of Di r r was obtained by solving eq. 1 fur the sta­tionary case (V - 0) and using the neasured values of d»(T). Fig. 4b shows this data for K<, - 10"3 dpa * s"1 along with the calculated dependence in the tranaltlon region /3,6/ derived for a vacancy migration energy of 0.75 eV. The stronger temperature dependence of the measured data is Interpreted In terns of a decrease In the sink strength with Increasing tenperature. This Is In agree­ment with the known behaviour of radiation Induced visible sinks like disloca­tion loops. This behaviour of D^ r r with T, In terns of the present nodel of particle growth, would lead to suaHer d. values with falling tenperature and would explain why nc precipitation could be detected below 500 K.

Conclusions:

1. Irradiation with 300 keV Cu + Ions produces Be-rlch precipitates In a CuBe alloy even at temperatures where the alloy Is undersaturated.

2. The growth kinetics of the precipitates could be quantitatively Interpre­ted In terns of a simple model for radiation Induced growth and dissolution.

3. Values for a) the effective diffusion coefficient of Be in Cu, b) the rate constant for cascade dissolution and c) point defect sink strength under irra­diation have been derived.

Ill A. Bartels, F. Dworschak, H.-P. Heurer, C. Abromjit and H. Wollenberger, J. Nucl. Mater. JJ3 (1979) 24

111 V. Naundorf, M.-P. Macht, H.-J. Gudladt and H. Wollenberger, Proc. Tamada Conf. V on Point Defects and Defect Interactions in Metals, eds. Takamura, J.I., Doyama, M. and Klritanl, M., University of Tokyo Press (1982) 934

131 R.P. Wahl, R. Koch, C. Abroneit and H. Wollenberger, to appear in J. Nucl. Mater.

/4/ A.D. Johnson and N.Q. Lam, Phys. Rev. B J^ (1976) 4364 151 R. Slznann, J. Nucl. Mater. 69 & 70 (1978) 386 16/ C. Abromelt and R. Poerschke, J. Nucl. Mater. Ji2_ (1979) 298

- 98 -

U J 1 ^

K0=10"2dpa s"1

0 10 20 Fluence [dpol

Fig . 1 F ig . 2

Fig. 1. Darkfield micrograph obtained with a precipitate reflection [KQ - 10"3 dpa s - 1, fluence - 2 dpa, T - 600 K]

Fig. 2. Average diameter d of precipitates as a function of fluence (Kg* t) in dpa

400 500 600 700 Irradiation Temperature TIKI

F lg .3 i

400 500 6O0 700 Irrodinrion Temperature TIKI

Fig.3b

•;/ f

A'' •is»- /} J </\ }, 1 1 ? # ' 1 1 /? ä

5 TO» TiiODK

S M 1 W 1 510* 10' Dc'ttt prMuctionrati K, [dpo i '1

Fig.4a

TIKI 170 6 » (30 W % 57S SS0 535 5D

»•

«r«

~~""--.^

IS H 17 11 I f 20 Flg.4b

Figs. 3a,b. Stationary value of the average precipitate diameter d» as a func­tion of temperature T. a) K„ » 5-10"* dpa-s - 1, b) K„ - 10"3 dpa-s"1

Figs. 4a,b. Effective diffusion coefficient D I r r as a function of a) defect production rate b) temperature

- 100 -

5.9. Microstructural Evolution in a Cu-1.35 at.% Be Alloy under Electron Irradiation in a High Voltage Microscope RR Wahi

Introduction

Investigations of the influence of 300 keV Cu+-ion irradiation on the micro-structural stability of a Cu-Be alloy have shown that the Irradiation causes rapid precipitation of the Incoherent 1 phase (CuBe), known to be the stable phase In the Cu-Be alloy system, under all irradiation conditions /1-3/. None of the coherent metastable phases, known to precede the formation of the stable phase under thermal conditions, have been reported. To investigate the influence of the nature of projectile particles on the microstructural evolution we have studied the same alloy (Cu-1.35 at.Z Be) after e~ Irradiations in a HVEH /*/. At the irradiation temperatures (600 K and 700 K;, the alloy is undersaturated under thermal conditions. The e~ flux density used corresponded to a defect pro­duction rate ~ 10~ 4 dpa/s"1.

Results and Discussion

Figs, la and b show the microstructure and a selected area diffraction (SAD) pattern, respectively, obtained after irradiation at 700 EC. The bright field (BF) micrograph in fig* la shows a tweed structure with striations lying parallel to the traces of {llO} matrix planes. The SAD pattern in fig. lb shows short streaks parallel to the <110> matrix directions. Radiation Induced dislo­cations could not be observed at any stage of irradiation at this temperature. These microstructural and diffraction characteristics are interpreted /4/ in terms of the formation of G.P. zones (Be-rich clusters).

Irradiation at 640 K resulted In rapid formation of dislocations in the form of clusters of Irregular shape (fig. 2a). Their density appeared to reach sa­turation after about 300 s. No tweed structure was observed at this temperatu­re. Careful examination of the specimen after irradiation, however, revealed thin contrast effects (fig. 2b) with their long axis at 90° to a matrix <200> direction. The corresponding SAD patterns showed a pair of weak extra reflec­tions with interplanar spacing d - 0.19 run. On the basis of Ashby and Brown cri­terion these contrast effects were identified aB vacancy type defects /4/. These could be one of the two known metastable phases y" or y 1 in this system known to have smaller atomic volume than that of the matrix. The measured interplanar spacing would fit to the structure of both these phases.

In the specimen irradiated at 600 K, a dense dislocation structure developed within a few seconds of irradiation (fig. 3a). The mlcrostructure after 2 * 10 s of irradiation showed the following characteristics:

- 101 -

(a) large Frank loops (» 70 nm In diameter) with characteristic stacking fault contrast and dislocation network.

(b) Very small (< 10 nm) dots with black/white contrast. Applying Thomas-Bell criterion these were also Identified as Frank loops /'•/•

(c) Contrast effects with roughly square geometry (fig. 3b). These could be ex­plained Ik/ as dislocation loops lying on (l00) planes with line vector "u I <011> and Burgers vector b II <100>.

The SAD patterns showed essentially matrix reflections without any form of streaking. A pair of weak extra reflections, however, was detected In patterns after 2 * 10 s of Irradiation. The corresponding d-spaclng was calculated to be 0.25 nm, which also fits to both y" and Y' phases.

These experiments show that mlcrostructural evolution under electron irra­diation (characterized by Individual point defect production) is essentially different frot that under Cu+-ion Irradiation (characterized by the formation of point defect cascades) even when comparable atomic production rates are employed in both cases. Whereas on Irradiation with Cu+-ions particles of the incoherent stable Y phase form directly bypassing the sequence of metastable phases, the electron irradiation results in the formation of Be-rich clusters (G.F. zones) and the metastable phases. The difference in the mlcrostructural evolution is rationalised /4/ on the basis of the different point defect sink configurations present in the alloy under the two types of Irradiations.

Ill R. Koch, R.P. Wahl and H. Wollenberger, J. Nucl. Mater. 103/104 (1981) 1211 111 R. Koch, Ph.D. Thesis (1983), D 83, Technical university Berlin 131 R.P. Wahl, R. Koch, C. Abromelt and H. Wollenberger, to appear In J. Nucl.

Mater. (1984) IUI R.P. Wahl and H. Wollenberger, J. Nucl. Mater. 1J2 (1983) 207

- 102 -

^m Fig. 1. a, BF micrograph in [lio] foil orientation and b, SAD pattern in [ lOO] foil orientation after = 10 3 s of irradiation at 700 K.

Fig. 2. a, BF micrograph showing dislocation clusters after about 6 x 10^ . of irradiation at 640 K. Foil orientation = [lio], b, DF m'crograph showing con­trast from two-dimensional defects after Irradiation ror 2 x 10 3 s at 640 K. Foil orientation = [21l].

F. 3. a, BF aid b, weak beam DF with g200 at S OO " ° after 2 x 10 3 s at 600 Ä. Contrast effects with square geometry clearly visible in b. Foil orienta­tion ~ [lOO].

- 103 -

5.10. Void Formation and Phase Stability under Heavy Ion Irradiation in Ferritic and Austenitic Alloys P. Dauben, J. Tenbrink and R. P Wan/

Ferritic and austenitic stainless steels represent candidate structural mate­rials for Tokamak type fusion reactors. Mechanisms of void formation and phase instability in these complex alloys are not well understood. Moreover there is a lack of data on the behaviour of these alloys under irradiation in the high fluence, e.g. 30-150 displacements per atom (dpa) regime.

In 1983, we have started, investigations of the above aspects of mlcrostructural evolution under irradiation on the following alloys:

1) Fe-12 at.Z Cr alloy, 11) ferritic steel 1.4914 and ill) austenitic steel 3161.. This programme is a part of EURATOM*s structural materials research and develop­ment programme in fusion technology. The alloys are Irradiated with 300 keV Fe"1" or Ni + ions which produce large displacement rates (up to 10" * dpa- s~l) enabling high fluences (up to 200 dpa) to be attained in reasonable times. To simulate the influence of large amounts of He gas production (~ 20 at.ppm/dpa) estimated to occur in stainless steel components in the first wall of the fusion reactors;

simultaneous injection of He + and the metal ions using a 'dual beam facility' is planned. This facility will go into operation by the end of 1984. In the mean­while, experiments have been performed on specimens preimplanted with He using 100 keV He + ions. All the implantations were carried out at the respective tem­peratures of the metal ion irradiations and the total dose of the implanted He was chosen as to maintain the above mentioned He/dpa ratio of 20. Figs. 1-3 show some typical bubble/cavity morphologies in the above alloys after irradiation. The ferritic alloys showed a larger resistance to cavity formation than the austenitic steel. In the former alloys, the cavities could be detected only in specimens preimplanted with He. Fig. 4 is a cavity map of the ferritic alloys showing the irradiation conditions under which bubbles/cavities form in these alloys. In the austenitic steel, cavities formed even in specimens which were not preimplanted with He.

- 104 -

Fig. 1 Fig. 2 Fig. 3

CAVITY FORMATION IN FERRITIC STEEL (~^\) AND FE-12 AT.X CR {///) ALLOY

600 K 700 K 800 K 900 K 1000 K 1100 K 1200 K i i i _ J i i i

lte+ + 30 dpa Fe +

He+ + 60 dpa Fe +

He+ + 100 dpa Fe +

He+ + 30 dpa Fe +

3D dpa Fe +

30 dpa Fe+

60 dpa Fe +

100 dpa Fe +

600 appm He

600 appm He

6000 appm He

Flg. 4

Fig. 1. Cavities in Fe-12 at.* Cr alloy after He implantation at 773 K.

Fig. 2. Cavities in Fe-12 at.X Cr alloy irradiated to 100 dpa with 300 keV Fe +

ions at 773 K a'ter Re preimplantation.

Fig. 3. Cavities in austenltic stainless steel 316L after irradiation to 150 dpa with 300 keV Ni+ ions at 900 K.

Fig. It. Experimental conditions for the formation of cavities in the ferritlc steel and the Fe-Cr alloy. In specimens preimplanted with He"*" and irradiated with Fe+> the He+/dpa ratio was maintained at 20. YES: cavities found, NO: no cavities found.

- 105 -

ZZZZMZ7.

0NO A^L

/ N 0

NO

YES

K W ^ > w > - s ^ ^ . V Y E S - X >j

6. HIGH TEMPERATURE FATIGUE OF SUPERALLOYS

6.1. Characterization of Precipitation Processes in Nimonic PE16 by T E M and the Correlation to Mechanical Properties H P. Degischer, H. Strecker and R P. Wahi

A research programme to investigate the high temperature deformation behaviour of the Nl-base alloy Nimonic PE16 has been started in cooperation with the Bun­desanstalt für Materialprüfung Berlin and the Technische Universität Berlin. The project Is financed by the Stiftung Volkswagenwerk. One of the aims of the pro­ject is the correlation of microstructure with mechanical behaviour. The micro-structural aspects of the investigations are being performed at the HMI. This paper reports on morphology and growth kinetics of precipitates on ageing.

The austenitic wrought alloy Nimonic PE16 is essentially composed of 00.06, Cr-16.5, M-43.5, Co<2.0, Mo-3.3, Ti-1.2, Al-1.2 wtZ and the rest FJ. The preci­pitation sequence and morphology as a function of annealing time t^ has been quantified:

a) Ti(C,N) is present in the material as primary inclusions of a few urn In diameter having a volume fraction of the order of 10~5.

b) TiC precipitates above 1100 K. The usual solution treatment around 1310 K yields carbides approximately 0.2 urn in diameter having a volume fraction of the order of 10"3.

c) M23C6 grain boundary carbides form between 900 K and 1150 K competing with the precipitation of TIC at the upper temperature limit. Aging treatments up to 1000 h below 1050 K produce M23C6 covering more than 10 % of the grain boundary area.

d) Nl3(Al,Ti) - Y* is known to precipitate between 900 K and 1120 K III, forming coherent spheres with a small lattice parameter misfit (3 x 10"*). The ordered structure of Ll2~type phase causes mainly the strengthening of the material. Imaging of -y' by TEM Is done best by dark field superlattlce reflection (fig. 1). Size-distribution, average diameters 3, particle density and volume fraction f have been determined after aging at 973 K, 1013 K, 1073 K and 1113 K up to 1000 h. The measured values in thin TEM-folls must be corrected to represent those in bulk material. Therefore a correction procedure was developed which also takes Into account the selective polishing attack at the particle - matrix Interface during specimen preparation 111. The growth of Y' - particles between 5 na and 90 urn was found 12! to obey © « t^n law, with 0.25 < n < 0.38 (fig. 2). The density of particles decreases with t "*. The volume fractions f (fig. 3) are below the values quoted by /3,4/ and do not show a dependence on ageing time. The growth of Y' within the investigated range can be understood as Ost-wald ripening and the measured size-distributions look similar to the theoreti­cally derlvated curves /5/.

- 106 -

isothermal microcalorlmetrlc measurements on samples quenched from solution temperature show a clear exothermal heat effect up to 973 K which vanishes af­ter a few minutes, whereas for air cooled specimens smaller,' faster decaying thermal effects are observed. This Indicates a rapid nucleatlon of precipitates starting already during air cooling.

So far the plastic behaviour has been studied by hardness measurements (HV 10). The Increase in hardness (normalized by the volume fraction of Y') exhibits a maximum at y' - particle diameters of about 20 nm (fig. 4). The differences in hardness in the overaged region indicate the influence of the carbides: M23C6 precipitation decreases above 1000 K.

The quantitative descripltlon of Y ' - precipitates and carbides serves as a basis for a mlcrostructural interpretation of the materials strength.

/I/ D. Raynor and J. M. Silcock, Metal Sei. (1970) 121 121 H.P. Degischer, H. Strecker, R.P. Wahl and H. Wollenberger, Proc. of the

8th European Congress on Electron Microscopy, Budapest (1984) 843 /3/ V. Martens and E. Nembach, Acta Met. TS_ (1:175) 149 /4/ B. Reppich, Acta Met. JJ0 (1982) 87 151 C. Wagner, Z. f. Elektrochemie 5_ (1961) 581

973 K / 16 h 0 « 9 nm 1113 K / 51 h 0 - 82 nm Fig. 1. Dark field images (superlattlce reflection) of y '-precipitates.

- 107 -

100 §v [nm]

10

0.1 1 10

Flg. 2. Coarsening kinetics of T'.

100 1000 t A I h 1

10 -f l%i -

r,3« •

•

• • ,|

• 1023 K 1073 K

• ** • • 5 •

U'3 K

1 • • '

1

' • 973 K . »1023 K

• 1073 K • »1113 K

•

A *

0,1 1 10

Fig. 3. Volume fraction f of the y '-phase. No time dependence could be observed.

100 1000 fothi

LÖV.

•

• •* • -— •

I 400

•

- m m —

• -— •

a

1 ^ •

~-T-200 • •

a

• 973 K

• • • 1073 K

_ 1 I ._ 1

* 1113 K

10 20 30 M) 50 9 [nm]

Fig. 4. Increase in hardness (HV 10) after annealing as function of 0, norma­lized by the volume fraction f. The temperature dependence indicates the in­fluence of carbides.

- 108 -

7. EXPERIMENTAL DEVELOPMENT. IMPLEMENTATION OF A FIELD ION MICROSCOPE . . _ R Mertens, U. Vidic and H. Becker

The field Ion microscope was developed to study the structure of alloys after thermal treatment and Irradiation with energetic particles- Exposed to the strong electrical fields in the Instrument especially the specimen tips for al­loyed materials are frequently destroyed. This short specimen life time as well as the aspired operating by unexperienced personnel and the restricted manpower avallabe for its construction provoked the following basic considerations far the Instrument's design:

requirements provisions easy maintenance

no liquid coolant for tip

reduction of LN2~use

high reliability and short repair periods

— temperature control by closed cycle refrige­rator

—' turbomolecular pumps instead of diffusion pumps

— use of commercial components wherever possible, instrument and support built of two easily detachable parts

easy operation

frequent and rapid tip exchan­ge for short-lived alloy spe­cimens FIM useable by unexperienced personnel daylight operation simple alignment and focusing

atom-probe operation indepen­dent of pulser type or time-dependent performance straightforward operation

easy data access and evaluation

five-tip-storage at 10"^ torr and electrical transport into tip holders

computer control for crucial functions (voltages etc.) video display of FIH-lmage electrostatic deflection plates, reasonably well focusing einzellens, focus control via rateaeter and additional video camera on-line pulse-height analysis of HV-pulses

large-scale computer control of the experi­ment, individual programs for atom-probe, desorption-nicroscope, and TOF-calibration instrument coupljd to a PDP 11/44 via UNIBUS, files stored on disks. On-line and off-line display of mess spectra and depth-distribu­tions

- 109 -

Mechanical hardware

In fig. 1 the main mechanical components of the Instrument are depicted. By Its three vacuum vessels the functions of the tip storage (up to five tips) and transport, tip Imaging and desorptlon and finally photographing and Ion detec­tion are performed. As the tips are stored at a pressure of typically 10"7 Torr the vacuum In the microscope Itself Is not noticeably deteriorated by changing the tips. By means of the xyz-manlpulator and eletrostatlc deflection plates In connection ulth a fairly performing Ion lens aligning the Instrument and focusing the ion beam are straightforward procedures. Field Ion image and the focus of the Ion beam are continuously displayed on video monitors enabling permanent control of the course of the experiment.

Electrical hardware

The electrical components including computer and CAKAC-lnttrumentation are sket­ched in fig. 2. Via the CAHAC-modules the voltages for the tip and the pulser can be set and read, the voltages for ion lens and imagine plates can be selec­ted, the digital delay can be chosen and a system status control performed. The high voltage pulse produced by the tip pulser is measured on-line and the result of this measurement is applied for calculating the mass of a desorbed ion. Using CAHAC-modules as well the flight time of the Ions is measured.

Software components

The programs for performing measurements with the field ion microscope are writ­ten in the Interpretative language HOHTI. Measuring programs for atom-probe ope­ration, field desorption and dynamic calibration of the mass spectrum are available. In spite of the large scale computer control of this experiment the operator has a variety of facilities to influence the course of a measurement. If desired the voltages applied to tip, pulser and ion lens can be set manually. By means of programmed interrupts the measurement can be interrupted or stopped, the display parameters can be changed etc. Graphic, display of mass spectra and depth profiles is Implemented. Enabled by this multitude of facilities the ope­rator at a computer terminal is completely informed of the progress of an expe­riment, as field ion image as well as a list of desorbed ions and the desired spectra are at his disposal on his desk. A compilation of the FIH operator's fa­cilities at atom probing are given in fig. 3.

- 110 -

Performance

The routine operation of this field Ion microscope started la 1982. Perfomance and reliability Met the aspired standards. No deterioration of the Imaging qua­lity due to possible mechanical vibrations connected Co the use of turbooolecu-lar pumps and a closed cycle refrigerator can be detected. The installation of video cameras allowing daylight operations significantly contributes to an easy and effective handling of the instrument. The mass resolution achieved in atom probing is fully sufficient to separate for example the neighbouring elements Fe, Ni and Cu. Enabled by the large scale computer control applied an operator really can concentrate on che experiment he is performing. The overall reliabi­lity of this field ion microscope is very satisfying. Typical failures being mostly related to the HV-pulse producing and pulae processing electronic equip­ment, operation can be in general instantaneously resumed after the replacement of the modulea In question. The vacuum system is opened less than twice a year for servicing the pumps or for applying minor modifications. Design and con­struction make Che instrument well suited for effective analysis of a large num­ber of specimens.

A detailed description of the FIH is available as HHI-report /l/.

I\l 0. Vidic, F. Hertens and H. Becker A Computer Controlled Field Ion Microscope With Atom Probe, HMI-Report

- Ill -

Flg. 1. The nechanical layout of the Instrunent.

FIELD ION MICROSCOPE

computer

CAMAC

experiment

Fig. 2. Block diagram of electronic supplies.

Fig. 3. Facil it ies in operating the field ion microscope.

- 113 -

III. PUBLICATIONS, DIPLOMA AND DR. THESES

PUBLICATIONS

In case of joint publications with external co-authors the publication Is listed under the nam* of the first HMI-author's name (underlined).

Abroaeit, C. and Uollenberger, H.: A Kinetic Model for Self-Interstitial Trapping at Solutes, Point Defect« and Defect Interactions in Metals, eds. J. Takanura, M. Doyaaa and M. Klritani (University of Tokyo Press, 1982) 349

Abromeit, C.: Comment on the Determination of Op from Damage-Kate Measurements J. Phys. F 12 (1983) L169

Abromeit, C. and Wollenberger, H.: Lattice Model for Self-Interstitial Trapping by Salutes Phil. Mag. A 47 (1983) 951

Krishan, K. and Abromeit, C.: Radiation Induced Instability in Concentrated Alloys J. Phys. F U (1984) 1103

MacEwen, S.R., Zee, R.R., Blrtcher, R.C. and Abromeit, C.: Point Defect Production and Annihilation in Neutron-Irradiated Zirconium J. Nucl. Mater. 122/123 (1984) 1036

Abromeit, C. and Krishan, K.: Radiation Induced Instability and its Influence on the Decomposition of a Concentrated Alloy, Proc. Conf. on Phase Stability and Phase Transformation Eds. Aaronson and Krishan, Bombay, Feb. 6 - 8 (1984)

Uecker, H., Riccato, A., Thacker, G.R., Ney, J. and Biersack, J.P.: Experiments on Sputtering of Niobium by 14 - 16 MeV Protons and Monte Carlo Calculations for Proton and Neutron Sputtering J. Nucl. Mater. 93/94 (1980) 670

Biersack, J.P. and Ecker, K.H.: Transmission Sputtering Experiments and Monte-Carlo Simulations, Proc. of the VII. Int. Conf. on Atomic Collisions in Solids, Moscow, (Moscow State Univ. Publ. House, 1980) 29

Biersack, J.P., Riccato, A. and Kaczerowakl, W.: TRIM Neutron Sputtering Calculations, Proc. of the Workshop on Sputtering Caused by Plasma Surface Interaction, Argonne, CONF-790775 (1980) 16-1

Biertack, J.P. and Raggmark, L.G.: A Monte Carlo Computer Program for the Transport of Energetic Ions in Amorphous Targets Nucl. Instr. Meth. 174 (1980) 257

115 -

Haggmark, L.G. and Mersack, J.P.: Monte Carlo Calculations of Light-Ion Sputtering as a Function of the Incident Angle J. Nucl. Mater. 93/94 (1980) 664

Blersack, J.P., Fink, D., Lauch, J., Henkelmann, R. and Miller, K.: An Instrument for Lattice Location Studies of Light Impurity Atoms by means of (n.a)-Reactlona. Nucl. Instr. Meth. 88 (1981), 411

Jahnel, F., Ryssel, H., Prinke, G., Hoffmann, K., Mliller, K., JJiersack, J.P. and Henkelmann, R.: Description of Arsenic and Boron Profiles Implanted In 3102, SI3N4 and SI using Pearson Distributions with Four Moments. Nucl. Instr. Meth. 182/183 (1981) 223

Blersack, J.P.: Calculation of Projected Ranges - Analytical Solutions and a Simple General Algorithm Nucl. Instr. Meth. 182/183 (1981) 199

Haggaark, L.G. and Mersack, J.P.: Sputtering Yield Calculations for Neutral Beam Particle Energies J. Nucl. Mater. 103/104 (1981) 345

Biersack, J.P.: New Projected Range Algorithm as Derived from Transport Equations Z. Phys. A 05 (1982) 95

Biersack, J.P. and Mertens, P.: Anomalies in the Thickness Dependence of the Energy Loss of Helium and Nitrogen Ions In Very Thin Carbon Foils, Proc. of the U.S.-Japan Seminar on Charged Particle Penetration Phenomena, (ORNL-Report, C'JHF-820131) 131

Ziegler, J.F., JJieraack, J.p. and Littmark, U.: Empirlal Stopping Powers for Ions in Solids, Proc. of the U.S.-Japan Seminar on Charged Particle Penetration Phenomena, (ORNL-Report, CONF-820131) 88

Biersack, J.P. and Ziegler, J.F.: The Stopping and Range of Ions in Solids IBM-Research Report RC 9380 (#41334) 5/10/82 (1982)

Biersack, J.P.: Refined Universal Potentials In Atomic Collisions Nucl. Instr. Meth. 194 (1982) 93

Jahnel, F., Mersack, J., Crowder, B. L., d'Heurle, F.M., Fink, D., Isaac, R.D., Lucchese, C.J. r.nd Petersson, CS.: The Behavior of Boron (also Arsenic) in Bilayers of Polycrystalllne Silicon <ind Tungsten Disllicide J. Appl. Phys. 53 (1982) 7372

- 116 -

Biersack, J.P. and Santner, E.: Sodium Hall de Sputtering by H+, He+, Ar + Ions Rad. Effects .64 (1982) 97

Biersack, J.F. and Ziegler, J.F.: The Calculation of Ion Ranges In Solids with Analytic Solutions Springer Series In Electrophyslcs, Vol. 10: Ion Implantation Techniques, Eds. H. Ryasel snd H. Glawlschnlg, Springer (1982)

Blersack, J.F. and Ziegler, J.F.: The Stopping and Range of Ions In Solids Springer Series In Electrophyslcs, Vol. 10: Ion Implantation Techniques, Eds. H. Ryasel and H. Glawlschnlg, Springer (1982)

Blersack, J.F. and Santner, E.: Sputtering of Alkali Halldes under Ion Bombardment Nucl. Instr. Meth. 98 (1982) 29

Biersack, J.F. and Stadele, M.: Repulsive Potentials and Nuclear Stopping in Ionic Insulators Rad. Effects 64 (1982) SI

Biersack, J.F.: He Profiles in Various Metals after Implantation and Thermal Anneals Rad. Effects 7S_ (1983) 363

Cowern, N.E.B. and Biersack, J.P.: Comparison of Theoretical Evaluations of Energetic Ion Range Distributions Nucl. Instr. Meth. 205 (1983) 347

Eckstein, W. and Biersack, J.P.: The Reflection of Light Swift Particles From Heavy Solid Targets J. Phya. A 3_10 (1983) 1

Biersack J.P.: Interaction Potentials and Stopping Powers of Heavy Ions, Proc. of the Padova Symp. on Applications of Accelerators in the Interdisciplinary Field, Padova, June (1984)

Jakas, M.M. and Bdersack, J.P.: Variational Calculation of Angular Width of the Multiple Scattering Distribution in Foil Transmission Z. Phys. A 31£ (1984) 29

Eckstein, W. and Blersack, J.P.: Sputtering Investigations with the Monte Carlo Program TRIM.SP Nucl. Instr. Meth. B 2_ (1984) 550

Blersack, J.P. and Eckstein, W.: Sputtering Studies with the Monte Carlo Program TRIM.SP Appl. Phys. A 34_ (1984) 73

Degischer, H.F., Strecker, H. and Wagner, W.: Imaging Weak Coherency Strains in CuCo, AlZr and Nimonic PE16 Alloys Proc. 8th European Congress on Electron Microscopy, Budapest (1984) 735

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Deglscher, H.P., Strecker, H., Wahl, R.P. and Wollenberger, H.: Determination of Size-Distribution and Volume-Fraction for T'-Precipitates in Nimonlc PE16 by TEM Proc. 8th European Congress on Electron Microscopy, Budapest (1984) 843

Ecker, K.H.: A Channelling Study of Defect-Impurity Complexes in Proton Irradiated Molybdenum (Cobalt) J. Nucl. Mater. U 9 (1983) 301

Ecker, K.H.: Displacement of Cobalt Impurities in Molybdenum (Cobalt) Studied by X-Ray Excitation with Channeled Protons Nucl. Instr. Meth. 3 2_ (1984) 747

Fink, D., Biersack, J.P. and Riederer, J.: Messung der Tiefenverteilung offener Poren in Festkörpern Berliner Beitrüge zur Archüometrie 5_ (1980) 99

Fink, D., Biersack, J.P., Riederer, J., Jahnel, F. and Henkelmann, R.: Bor und Lithium in antiker und moderner Keramik Berichte der Dt. Keramischen Gesellschaft (1980)

Fink, D., Biersack, J.P., Jahnel, F. and Henkelmann, R.: Untersuchung von Helium, Lithium und Bor in Metallen mit Hilfe von (n,p) und (n,a)-Reaktlonen. Analysis of Nön-Metals in Metals, ed. G. Kraft, Walter de Gruyter & Co., Berlin, Uew York (1981) 163

Fink, D. and Riederer, J.: Studies of Li, B and N in Ancient Oriental Pottery and Modern Ceramic Materials by means of (n,p) and (n,ct) Spectrometry Nucl. Instr. Meth. 1_9_1 (1981) 408

Fink, D., Biersack, J.P., Lauch, J., Jahnel, F., Müller, K. and Henkelmann, R.: Bestimmung von Gitterpositionen von Lithium und Bor alt Hilfe von (n,a)-Reaktlonen mit thermischen Neutronen Bericht d. Verbundes 'Komplementäre Methoden und Defekte', Konstanz, (1981) 106

Fink, D., Biersack, J.P., Tjan, K. and Cheng, V.R.: Ranges of 3He and 6Li In Various Solids Nucl. Instr. Meth. 94 (1982) 105

Fink, D., Biersack, J.P., Riederer, J., Jahnel, F. and Henkelmann, R.: Bor and Lithium in antiker und moderner Keramik Sprechsaal _115_ (1982) 513

Fink, D. and Biersack, J.P.: Catastrophic Sputtering of Sulfur by Helium Rad. Effects 64 (1982) 89

Fink, D. and Riederer, J.: Bor-, Lithium- und Stickstoffgehalt von antiker nahb'stlicher Keramik Berliner Beiträge zur Archäometrie ]_ (1982) 203

- 118 -

Fink, D., Biersack, J.P. and Liebl, H.: Background In (n,p) and (n,a) Spectrometry Springer Series In Electrophysics, Vol. 11: Ion Implantation: Equipment and Techniques, eds. H. Ryssel and H. Glawlschnlg, Springer (1983)

Fink, D., Biersack, J.P., Carstanjen, H.D., Jahnel, F., Müller, K., Ryssel, H. and Osel, A.: Studies on the Lattice Position of Boron In Silicon Rad. Effects 2Z (1983) 11

Fink, D., Biersack, J.P., Städele, H., Tjan, K. and Cheng, V.K.: Nitrogen Depth Profiling Using the 14N(n,p)l4C Reaction Nucl. Instr. Meth. 2JJL (1983) 171

Fink, D., Biersack, J.P., Städele, M., Tjan, K. and Cheng, V.K.: 22 Stopping Power Oscillations as Derived from Range Measurements Nucl. Instr. Meth. 18 (1983) 817

Fink, D.: Li, B and N in Ancient Materials Nucl. Instr. Meth. 118 (1983) 456

Fink, D., Biersack, J.P., Städele, M., Tjan, K., Harlng, R.A. and De Vrles, A.E.: Experiments on the Sputtering of Group VI Elements Nucl. Instr. Meth. B l_ (1984) 275

Fink, D., Chen, J.T., Biersack, J.P., Siedele, M., Tjan, K., Schlosser, S. and Stumpff, C.: Distribution of Light Ions and Foil Destruction after Irradiation of Organic Polymers, Proc. 1984 Conf. Meeting of the Materials Research Society Europe, Straflburg, June 5-8 (1984)

Fink, D., Behar, M., Biersack, J.P., Carstanjen, H.D., Städele, M. and Zawislak, F.: Complementary Ose of Nuclear Reaction Analysis with Thermal Neutrons and Conventional Ion Beam Analysis Techniques for Applications in Electronics, Fusion Research and Space Technology, Proc. of the Padova Symp. on Applications of Accelerators in the Interdisciplinary Field, Padova, June (1984)

Gulling, H.W., Poerschke, R., Schwann, D. and Wollenberger, H.: Diffuse and Small Angle Neutron Scattering Studies of Clustering and Decomposition in Electron-Irradiated CuNiFe Alloys, Proc. Int. Conf. on Phase Transformations in Solids, Crete, 1983 Ed. T. Tsakalakos, Materials Research Society 21 (1984) 583

Gudladt, H.-J., Naundorf, V., Macht, M.-P., and Wollenberger, H.; Past Interstitial-Solute Complex Diffusion under Irradiation in CuBe J. Nucl. Mater. 118 (1983) 73

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Gudladt, H.-J., Koch, R., Macht, M.-P., Naundorf, V., Wahl, K.P. and Wollenberger, H.: Be Diffusion Coefficient and Y Precipitation Growth Rate in Self-Ion Irradiated Dilute CuBe Alloy«, Proc. Conf. on Dimensional Stability and Mechanical Behaviour of Irradiated Metals and Alloys, Brighton, 1983 British Nuclear Energy Society, London, 1_ (1984) 31

Hein, W., Wagner, V., Wollenberger, H. and Juul Jensen, D.: Saall Angle Neutron Scattering Study of f'-Precipitation in N1A1T1, Sth Rise' Int. Syap. on Mlcrostructural Characterization of Materials by Non-Microscopical Techniques, Ri.skilde, Denmark, Sept. (1984) 279

Koch, R., Wahl, R.P. and Wollenberger, H.: TEM-Investigatlon of the Mlcrostructural Evolution in Simulation-Irradiated CuBe Alloys J. Nucl. Mster. 103/104 (1981) 1211

Koch, R., Wahl, R.P. and Wollenberger, H.: Formation of Precipitates under Irradiation in an DnderBaturated CuBe Alloy Inst. Phys. Conf. Ser. No. 66, EMAG, Guildford, UK, (1983)

Krist, Th. and Hertens, P.: Proton Energies at the Maximum of the Electronic Stopping Cross Section in Materials With 57 < z 2 < 83 Nucl. Instr. Math, 2Q (1983) 790

Krist, Th. and Mertens, P.: Stopping Ratios for 30 - 330 keV Light Ions In Materials with 57 < Zj < 33 Nucl. Instr. Meth. 218 (1983) 821

Krist, Th. and Mertens, P.: Application of Brandt's Effective Charge Theory to Measurements for 50 - 350 keV Ions with 1 < Zy < 5 Nucl. Instr. Meth. B 2_ (1984) 119

Krist, Th., Hertens, P. and Biersack, J.P.: Nuclear Stopping Power for Particles Transmitted through Thin Foils in the Beam Direction Nucl. Instr. Meth. B 2_ (1984) 177

Macht, M.-F. and Naundorf, V.: Direct Measurement of Small Diffusion Coefficients with Secondary Ion Mass Spectroscopy J. Appl. Phys. 53 U*82) 7551

Macht, M.-F., Naundorf, V. and DBhl, R.: Measurement of Small Diffusion Coefficients with SIMS in Metals and Alloys, DDfETA 82, Diffusion in Metals and Alloys, eds. F.J. Kedes and L. Bleke Diffusion and Defect Monograph Series Transtech. Publications Switzerland, 7 (1983)

- 120 -

Macht, M.-P. Naundorf, V., Wahl, R.P. and Wollenberger, H.: Investigation of Chemical Redistribution In Dllute Cu-Alloys under Simulation Irradiation J. Nucl. Mater. 122/123 (1984) 698

Macht, M.-P. and Naundorf, V.: HochauflSSsende Analyse der Dlffusiou in Hc' llen Phys. Bl. 40 (1984) 9

Hertens, P. and Conrad, R.: A Microprocessor-Based Beaa Sweep Control Unit. Nucl. Instr. Math, _189 (1981) 275

Mertens, P. and Krist, Th.: Stopping Ratios for 30 - 330 keV Ions with 1 < Z t < 5 J. Appl. Phys. 53_ (1982) 7343

Mertens, P. and Krise, Th.: Energy Loss of 300 keV He + and N+ in 150 to 800 A Carbon Foils Phys. Rev. B 25_ (1982) 5591

Mertens, P. and Krist, Th.: Electronic Stopping Cross Sections for 30 - 300 keV Protons in Materials with 23 < Z 2 < 30 Nucl. Instr. Meth. JJM (1982) 57

Vogl, G., Miekeley, W., Heidemann, A. and Petry, W.: Anomalously Fast Diffusion of Cobalt in 8-Zirconlum: Evidence for Two Diffe­rent Jump Frequencies fron Quasielastic Neutron Scattering Phys. Rev. Letters 53 (1984) 934

Müller, M.: Investigation of Radiation Induced Defect Impurity Conplexes in Aluminium Alloys by Channeling. A Critical Analysis by Computer Simulation. Nucl. Instr. Meth. 213_ (1983) 453

Naundorf, 7., Macht, M.-P., Gudladt, H.-J. and Wollenberger, H.: Measurement of Radiation Induced Impurity Diffusion in Copper, Point Defects and Defect Interactions in Metals, eds. J. Takamura, M. Doyama and M. Kiritani (university of Tokyo Press, 1982) 934

Naundorf, V. and Abromeit, C.: Effective Defect Production Rate for Pulsed Irradiation Rad. Effects 69 (1983) 261

Piller, J., Wagner, U., Wollenberger, H. and Mertens, P.: Thermal Decomposition in CuNiFe Alloys I. Field Ion Microscope and Atom Probe Investigation, Froc- Int. Conf- on Early Stage Decomposition, Sonnenberg 1983, to appear in Scripta Met. (1984)

Poerachke, R., Wagner, W. and Wollenberger, H.: Radiation Induced Interdiffusion and Phase Transformation in Electron Irradiated CuNi Alloys, Point Defects and Defect Interactions in Metals, eds. J. Takamura, M. Doyama and M. Kiritani (University of Tokyo Press, (1982) 938

- 121 -

Poerschke, R. and Schwann, D.: Radiation Enhanced Diffusion as n Tool for Alloy Decomposition Studies at Low Temperatures: Neutron Scattering on Electron Irradiated CuNi Alloys, Proc. Int. Conf. on Early Stage Decomposition, Sonnenberg 1983, to appear in Scripta Met. (1984)

Poerschke, R., Calling, H.H., Wagner, W. and Wollenberger, H.: Irradiation Induced Decomposition In CuNlFe Alloys, Proc. Conf. on Phase Transformators and Phase Stability, eds. Aaronson and Krlshan, Bombay, Feb. 6-8, (1984)

Poerschke, R., Gulling, H.H., Schwahn, D., Wagner, W. and Wollenberger, H.: Neutron Scattering Studies of Short Range Clustering and Long Range Decomposition in CuNlFe Alloys, 5th Riss' Int. Symp. on Hlcrostructural Characterization of Materials by Non-Microscopical Techniques, Roskilde, Denmark, (1984) 425

Thels, U. and Wollenberger, H.: Mobile Interstltials Produced by Neutron Irradiation in Copper and Aluminium J. Hud. Mater. 88_ (1980) 121

Renn, L.E., Wagner, W. and Wiedersich, H-: Radiation-Induced Segregation in Concentrated CuNl Alloys Scripta Met. 15 (1981) 683

Wagner, W., Poerschke, R. and Wollenberger, H.: Dependence of Electrical Resistivity on the Degree of Short Range Order in a Nickel Copper Alloy Phil. Mag. B 43 (1981) 345

Averback, R.S., Reha, L.E., Wagner, W., Okamoto, P.R. and Wiedersich, H.: In Situ Rutherford Backscattering Analysis of Radiation-Induced Segregation Nucl. Instr. Meth. 194 (1982) 457

Rehn, L.E., Okamoto, P.R., Averback, R.S., Wagner, W. and Wiedersich, H.: Effect of Defect Production Rate on Radiation-Induce ' "—gregation Scripta Met. i (1982) 639

Wagner, W., Rehn, L.E. and Wiedersich, H.: Near-Suriace Segregation In Irradiated NI3SI Phil. Mag. A 5 (1982) 957

Wagntr, W., Naundorf, V., Rehn, L.E. and Wiedersich, H.: Surface Segregation in Concentrated NiCu Alloys Under Irradiation, Proc. of the 11th Conf. on Effects of Radiation on Materials, eda. H.R. Brager and J.S. Psrrin, American Society for Testing and Materials, (1982) 895

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Wagner, W., Foei.-chke, R. and Wollenberger, H.: Short-Range Clustering and Long-Range Periodic Decomposition of an Electron Irradiated NlCu alloy J. Phys. F J12 (1982) 405

'erback, R.S., Rehn, L.E., Wagner, W., Wiedersich, H. and Okamoto, P.R.: Kinetics of Radiation-Induct4 Segregation in Ni-12.7 at.Z Sl Phys. Rev. B 28, (1983) 3100

Wagner, W., Rehn, L.E., Wiedersich, H. and Naundorf, V.: Radiation-Induced Segregation in NlCu alloys Phys. Rev. B £8 (1983) 6780

Wagner, W., Poerschke, R. and Wollenberger, H.: Thermal Decomposition in CuNiFe Alloys. III. Neutron Diffraction Study, Proc. Int. Conf. on Early Stage Decomposition, Sonnenberg 1983, to appear in Scripta Met. (1984)

Wagner, W., Piller, J., Poerschke, R. and Wollenberger, H.: Theroal Decomposition in CuNiFe Alloys. A Comparative Study Combining Microscopical and Non-Microscopical Techniques, 5th Risrf Int. Symp. on Microstructural Characterization of Materials by Non-Microscopical Techniques, Roskilde, Denmark, (1984) 551

Wahl, R.P. and Ilschner, B.: Fracture Behaviour of Composites Based on A1203-T1C J. Mater. Sei. 15_ (1980) 875

Wahl, R. P.: Presipltatio. „z .hin Foils of an FeNiCr Alloy Scripta Met. 14_ (1980) 122?

Wahl, R. P.: Fracture Behaviour of Two-Phase Ceramic Alloys Based on Aluminium Oxide. Transactions of the Indian Institute of Metals V*. (1981) 89

Wahl, R. P. and Wollenberger, H.: Microstructural Evolution in a Cu-1.35 at.Z Be Alloy under Electron Irradiation in a High Voltage Microscope J. Nucl. Mater. JL13_ (1983) 207

Wahl, R. P. and Stajer, J.: Thermal Decomposition in CuNiFe Alloys. II. A TEM Investigation, Proc. Int. Conf. on Early Stage Decomposition, Sonnenberg 1983, to appear in Scripta Met. (1984)

Wollenberger, H., Dworschak, F. and Holfelder, G.: Damage Rates in Electron Irradiated Au and Dilute AuFe Alloys

' Rad. Effects 9_ (1981) 35 Wollenberger, H.:

Materietransport unter Bestrahlung Z. Mctallkde 21 (1981) 608

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Bartels, A., Bewerungc, J., "Dworschak, F. and £ollenberger, H.: Solutes In Copper as Nuclei for Self-Interstitial Complexes J. Phys. F 12 (1982) 641

Bartels, A., Bcwerunge, J., Dworschak, F. and Wollenberger, H.: Spontaneous Recombination of Single Vacancies and Clustered Interstltiala in Copper Rad. Effects Letters 6]_ (1982) 135

Wollenberger, H.: Interstitialcy Transport in Dilute Alloys under Irradiation, Point Defects and Defect Interactions in Metals, eds. J. Takamura, M. Doyame and M. Kiritanl (University of Tokyo Press, 1982) 339

Wollenberger, H.: Point Defects Chapter 17, Physical Metallurgy, third, revised and enlarged edition, R.W. Cahn and P. Haasen, eds., Elsevier Science Publishers BV, Amsterdam, (1983)

Wollenberger, H., Abromeit, C. and Dworschak, F.: Self-Interstitial Solute Interaction in Aluminium Base Alloys: Problems of Data Interpretation Rad. Effects 22 (1983) 255

Wollenberger, H.: Irradiation-Driven Phase Transformations In Alloys Ber. Bunsenges. Phys. Chen. 87_ (1983) 229

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DIPLOMA THESES

Dauben, P.:

TEH-Unterauchuiigen der Bildung von Versetzungen in Kupfer-Nickel­legierungen unter Cu+-Ionen-Beatrshlunj May 1982, Tu B«rlin

DShl, R.: Messung des Diffuslonskoef£izienten von Co in Cu zwischen 640 K und

848 K

October 1982, TU Berlin

Kophaael, B.:

Verhalten dea elektrischen Restwiderstandes von Kupfer-Nickel-Legie­

rungen bei Entmischungen durch 3 MeV Elektronenbestrahlung

July 1982, TO Berlin

Lang, R.:

feldionenaikroskoplsche Untersuchung der Karbidbildung in Eisen-Chron-

Leglerungen

July 1984, TU Berlin

DR. THESES

Gudladt, H.-J.:

Untersuchung der Frendatondiffusion in Kupfer unter Selbstionenbestrah­

lung

September 1983, TU Berlin

Koch, R.:

GefUgeentwlcklung einer Cu-1,35 At.Z Be-Leglerung unter Schwerlonenbe-

strahlung

August 1983, TU Berlin

Krist, Th.:

Energieverlustaesaungen an leichten Ionen in Metallfolien

August 1982, FU Berlin

StXdcle, H.:

Universelle Darstellung repulsiver Potentiale, nuklearer Bremsveraögen

und projizierter Reichwelten

April 1983, FU Berlin

- 125 -

IV. HMI-REPORTS, PATENT APPLICATIONS

HMI-REPORTS

Biersack, J.P.: Calculation of Projected Ranges - Analytical Solutions and a Simple General Algorithm HMI B 33* (1980)

Jahn, G.: Probleme der Wärmeübertragung bei der Bestrahlung von Festkörpern HMI B 349 (1981)

Herdam, G. and Poerschke, R. : Rechnerunterstützt« Messung des elektrischen Widerstandes elektronen­bestrahlter Metalle HMI B 390 (1983)

PATENT APPLICATIONS

Jahn, G. and Friedrich, G.: Flüssigstickstoff (LN2)~Abf.üllstation mit zwei Entnahmestellen, automatische Abfüllung und Handabflillung know-how Angebot (September 1982)

Jahn, G. and Schultheis, G.: Auswechselbare Folienfeu.ster mit integrierter Dichtscheibe für Elektronenbestrahlungseinrichtungen Applied for in the Fedural Republic of Germany (June 1982)

- 126 -

V. LECTURES, UNIVERSITY LECTURES

LECTURES

Abromelt. C.: Phisenstabllltät unter Einfluß von Bestrahlung Werkstoff Colloquium der GfK Karlsruhe, Karlsruhe, 3.7.81

AbroMlt, C.: A Kinetic Model for Self-Interstitial Trapping at Solutes Yamada Conf. on Point Defects and Defect Interaction In Metals, Kyoto, Japan, 19.11.81

Abroaelt, C.: Models of Stability of Precipitates under Irradiation Materials Science Laboratory, Reactor Research Centre, Kalpakkam, India, 10.12.81

Abrosttit, C. and Wollenberger, H.: A Kinetic Model for Self-Interstitial Trapping at Solutes DAE Symp. on Crystal Lattice Defects and Defect Interactions, Varanasl, India, 22.1.82

Abromelt, C : Models of Stability of Precipitates under Irradiation Metallurgy Division, Bhabha Atomic Research Centre, Bombay, India, 18.2.82

Abromeit, C.: Bestrahlungslnduzlerte Instabilität in konzentrierten Legierungen Freie Universität Berlin, 15.4.82

Abromeit, C. and Krishan, K.: Radiation-Induced Instability In Concentrated Alloys Gordon Research Conf. on Physical Metallurgy, Andover, N. H., USA, 13.7.82

Abromeit, C : Models for Self-Interstitial Trapping at Solutes Chemistry and Materials Division, AECL Chalk River, Canada, 16.8.83

Biersack, J.p.: BremsvermSgen und Reichweiten - unser heutiges theoretisches Verständnis Inst, ftir Angewandte Physik der Universität Erlangen, 13.10.80

Biersack, J.P.: Repulsive Potentials In Atomic Collisions and their Applications In Scat­tering and Stopping Theory Nlels-Bohr-Inst., Copenhagen, Denmark, 4.11.80

Biersack, J.P.: Principal Problems in the Calculation of Projected Range Distributions R.C. Oersted-Inst., Copenhagen, Denmark, 7.11.80

Biersack, J.p.: Studies on Range and Damage Distribution of Light Ions in Solids Interunlversltalr Reactor Instituut Delft, Holland, 27.11.80

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Biersack, J.P.: Recent Work on Interatomic Potentials and Stopping Powers Centro Atöalco Bariloch«, Argentina, 22.12.80

Biersack, J.P.: A New Projected Range Algorltha and its Derivation from Transport Equations Centro AtSaico Barilochc, Argentina, 23.12.80

Biersack, J.P.: Atomic Collisions in Solids Unlversidad Tecnica, Santiago de Chile, Chile, 7.1.81

Biersack, J.P.: Stopping Powers and Ranges Universldad Catolica, Santiago de Chile, Chile, 9.1.81

Biersack, J.P.: Plasma-Wall Interaction in Fusion Devices Universldad de Chile, Santiago de Chile, Chile, 12.1.81

Biersack, J.P.: Does an Universal Repulsive Potential exist in Atomic Collisions? Vth Int. Conf. on Ion Beaa Analysis, Sydney, Australia, 19.2.81

Biersack, J.P.: Direct Derivation of Differential Equations for Projected Range Distribu­tions Vth Int. Conf. on Ion Beaa Analysis, Sydney, Australia, 19.2.81

Biersack, J.P.: Recent Developments in Stopping and Range Theory RHIT Melbourne, Australia, 25.2.81

Biersack, J.p.: The Use of the (n,a) Nuclear Reaction for Depth Profiling and Lattice Loca­tion Studies Tandem Accel. Lab., Uppsala, Sweden, 15.6.81

Bleraack, J.P.: Sputtering of Alkali Halides by Ion Irradiation Nordic Syap. on Ion Induced Desorption, Uppsala, Sweden, 16.6.81

Biersack, J.P.: The Influence of Atomic Charge States on the Repulsive Potentials in Atomic Collisions Int. Conf. on Radiation Effects in Insulators, Arco di Garda, Italy, 30.6.81

Biersack, J.P.: Potassium Ralide Sputtering by H+, He +, Ar + Ions Int. Conf. on Radiation Effects in Insulators, Arco Jl Garda, Italy, 30.6.81

Biersack, J.P.: New Universal Potentials in Binary Collisions 9th Int. Conf. on Atomic Collisions in SolidB, Lyon, France, 6.7.81

- 128 -

Biersack, J.P.: A Universal Interatomic Potential based on Solid State Charge Distributions 9th Int. Conf. on Atomic Collisions in Solids, Lyon, France, 6.7.81

Biersack, J.P.: Ranges of 3He, 6 U and 1 0B in Various Solid* 9th Int. Conf. on Atonic Collisions in Solids, Lyon, France, 9.7.81

Biersack, J.P.: Hew Projected Rang« Algorithm as derived from Transport.Equations 9th Int. Conf. on Atomic Collisions in Solids, Lyon, France, 9.7.81

Blersack, J.P., Jahne1, F., Henkelmann, R. and Fink, D.: Range Distributions of Ion Implanted 1 0 B in Al, T, V, Co, Zr and Au 9th Int. Conf. on Atomic Collisions in Solids, Lyon, France, 9.7.81

Biersack, J.P.: Sputtering Yield Calculations for Neutral Beam Particle Energies Second Topical Meeting on Fusion Reactor Materials, Seattle, USA, 11.8.81

Biersack, J.P., Jahnel, F., Fink, D., D'Heurle, F., Isaac, R., Luchese, C. and Peterson, S.: The Behaviour of B (also As) in Bilayers of Polysilicon and WSi2 11th European Solid State Device Research Conf., Toulouse, France, 14.9.81

Biersack, J.P.: Potentiale und Abbremsverhalten niederenergetischer schwerer Ionen II. Physikalisches Inst., Universität Göttingen, 13.11.81

BierBack, J.P., Ziegler, J.F. and Littmark, U.: Empirical Stopping Powers for Ions in Solids US/Japan Seminar on 'Charged Particle Penetration Phenomena', Honululu, USA, 26.1.82

Biersack, J.P. and Mertens, P.: Anomalies in the Thickness Dependence of the Energy Loss of Helium and Nitrogen Ions in Very Thin Carbon Foils 26.1.82

Biersack, J.P.: The Sputtering Mechanisms in Ionic Crystals IBM Watson Research Center, Yorktowa Heights, New York, USA, 23.3.82

E'ersack, J.P.: Sputtering Predictions on the Fusion First Wall Materials Titanlumcarbide and Titaniumboride in Comparison to Experimental Data, AVS Meeting in San Diego, California, USA, 8.4.82

Biersack, J.P.: Investigation of Prefential Sputtering with the Monte-Carlo Code TRIM Electronic Engineering Department, Inst, of Technology, Pasadena, California, USA, 16.4.82

Biersack, J.P.: Energieverluste und Reichweiten niederenergetischer Ionen in Festkörpern Sektion Physik, Friedrich-Schlller-UniversitSt, Jena, DDR, 10.6.82

- 129 -

Biersack, J.P.: Recent Theoretical Studies on Interatomic Potentials Int. Workshop on 'Analytic Methods in Radiation Effects', Polop de la Marina, Spain, 29.6.82

Blersack, J.P. and Stidele, M.: Interatomic Potentials Based on Overlapping Lenz-Jensen Atoms and Its Ana­lytical Representations Int. Workshop on 'Analytic Methods In Radiation Effects', Polop de la Marina, Spain, 29.6.82

Blersack, J.P. and Covern, N.: The Exact Shape of High Energy Particle Range Distributions Int. Workshop on 'Analytic Methods In Radiation Effects', Polop de la Marina, Spain, 30.6*82

Blersack, J.P.and Eckstein, W.: The Backscatterlng of High Energy Light Ions Int. Workshop on 'Analytic Methods in Radiation Effects', Polop de la Marina, Spain, 30.6.82

Bieraack, J.P.: Analytical Method In Calculating Scattering Angles, Energy Transfers and Nuclear Stopping Powers Int. Workshop on 'Analytic Methods In Radiation Effects', Polop de la Marina, Spain, 30.6.82

Biersack, J.P. and Krüger, W.: Transformation of the Backward Boltzmann Equation into the Volterrc Integral Equation for a Direct Commutation of the First Four Moments of Range Distributions Int. Workshop on 'Analytic Methods in Radiation Effects', Polop de la Marina, Spain, 1.7.82

Blersack, J.P.: The New Projected Range Algorithm and its Potential for Analytial Solutions Int. Worksttcp on 'Analytic Methods In Radiation Effects', Polop de la Marina, Spaiu, 1.7.82

Blersack, J.P.: Analytic Results fot Ion Ranges in Solid Targets Int. Workshop on 'Analytic Methods in Radiation Effects', Polop de la Marina, Spain, 8.7.82

Biersack, J.P.: A Universal Repulsive Potential Based on Overlapping Realistic Atoms Int. Conf. on 'Ion Beam Modification of Materials', Grenoble, France, 6.9.82

Blersack, J.P., Ziegler, J.F., and Littaark, II.: Stopping Powers for Low Energy Ions in Solids Int. Conf. on 'Ion Beam Modification of Materials', Grenoble, France, 8.9.82

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Biersack, J.P. and Ziegler, J.F.: The Stopping and Range of Ions in Solids IVth Int. Conf. on Ion Implantation, Berehtesgaden, 13.9.82

Biersaclt, J.P. and Ziagler, J.F.: The Calculation of Ion Ranges in Solids with Analytical Solutions IVth Int. Conf. on Ion Implantation, Bf>rchtesgaden, 13.9.82

Biersack, J.p.: The Projected Range Algorithm PRAL <.ad its Solutions for Elemental and Multicomponent Targets IVth Int. Conf. on Ion Implantation, Bsrchtesgaden, 14.9.82

Biersack, J.P.: Helium Profiles In Various Metals after Implantation and Thermal Anneals Int. Workshop on Helium In Metals, Jülich, 23.9.82

Biersack, J.P.: Realistic Repulsive Potentials, Stopping Powers and Ranges for Low Energy Ions In Solids AECL Chalk River, Ontario, Canada, 16.11.82

Blersack, J.P.: New Potentials and Stopping Powers for Calculating Ion Range Distributions in Solids Stanford University, California, USA, 29.11.82

Biersack, J.P.: Analytical Methods In Stopping and Range Theory Sandle Laboratories, Uvermore, California, USA, 1.12.82

Biersack, J.P.: The Ion Transport Code TRIM and Its Physical Foundations Research Inst, of Physics, Stockholm, Sweden, 14.12.82

Biersack, J.P.: Recent Progress in Stopping and Ranges of Ions in Solids Inst, de Flslca, UFRGS, Povto Alegre, Brazil, 16.3.83

Biertack, J.P.: Atomic Collisions In Solids Inst, de Flslca, UFRGS, Porto Alegre, Brazil, 8.3. till 7.4.83

Biersack, J.P.: New Results In Electronic and Nuclear Stopping Inst, de Flslca, PUC, Rio de Janeiro, Brazil, 15.4.83

Blersack, J.P.: Recent Theoretical Developments in Electronic Stopping and Projected Ranges Inst, de Flslca, USP, Sao Paulo, Brazil, 20.4.83

Blersack, J.P.: Abbrsmsung und Transport energetischer leichter Ionen In Metallen KFA Jülich im DFG-Schwerpunkt "Fusionsorientierte Plasmaphysik", 10.5.83

- 131 -

Biersack, J.P.: Differential Equations for Projected Ranges and Universal Analytical Solu­tions Int. Conf. on Ion Baaa Analysis, Temp«, Ariz., USA, 23.S.83

Biersack, J.P.: Range Distributions of Ions In Solids Int. Conf. on Ion Beam Analysis, Teape, Ariz., USA, 26.S.83

Biersack, J.P.: Recant Developments In the Colllslonal Theory of Defect Production and Sputtering Int. Conf. on Radiation Effects In Insulators, Albuquerque, USA, 30.5.83

Biersack, J.P.: Ion Implantation In Theory and Experioent Cornell University, Ithaca, New York, USA, 7.6.83

Biersack, J.P.: Sputtering of Insulators IBM Watson Research Center, Yorktown Heights, New York, USA, 10.6.83

Biersack, J.P.: Wachselwirkung leichter Ionen nit mehrkomponentigen Festkörpern • Universität Köln, 27.6.83

Biersack, J.P.: Physik der atomaren Stöße und ihre Anwendung auf Oberflachenzerstäubung, Strahlenschilden und Implantation Universität Huppertal, 29.6.83

Biersack, J.P. and Eckstein, W.: Sputtering Investigations with the Monte-Carlo Program TRIM.SP Int. Conf. on Atomic Collisions In Solids, Bad Iburg, 21.7.83

Biersack, J.P.: Light Ion Sputtering of Metals and Low Z Compounds as studied with the Monto-Carlo Code TRIM Vth Int. Solid Surface Conf. and 9th Int. Vacuum Congress, Madrid, Spain, 30.9.83

Biersack, J.P.: Atomic Collisions, Ion Implantation and Radiation Effects In Solids Shanghai Inst, of Metallurgy, Academy of Sciences of China, Shanghai, China, 24.10. till 1.11.83

Biersack, J.P.: Recent Developments in Stopping and Unge Theory Inst, of Semi-Conductors, Peking, China, 31.10.83

Biersack, J.P.: Recent Progress in Stopping and Range Theory Inst, of Nuclear Physic, Academy of Sciences of China, Jarding, China, 2.11.83

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Biersack, J.P.: Uses of the TRIM Program Inst, of Metallurgy, Acadeny of Sciences Shanghai, Shanghai, China, 1.11. till 4.11.83

Biersack, J.P.: The Honta-Carlo Code TRIM and Its Applications RMIT Melbourne, Australia , 15.11. and 16.11.83

Biersack, J.P.: Stopping and Hanges of Ions In Solids CSIRO, Clayton, Australia , 22.11.83

Biersack, J.P.: Repulsive Potentiale in Atomic Collisions University of Newcastle, Australia , 30.11.83

Biersack, J.P.: Ion Implantation in Semi-Conductors University of New South Wales, Sydney, Australia , 3.12.83

Biersack, J.P.: Interaction Potentials and Stopping Power of Heavy Iona Int. Workshop on New Use of Accelerators, Legnaro, Padua, Italy, 31.5.84

Biersack, J.P.: TRIM - its Physical Background and its Application AERE, Harwell, UK, 26.6.84

Biersack, J.P.s The Binary Collision Code TRIM Inst, of Phys., London, UK, 27.6.84

Biersack, J.P.: The New Projected Range Algorithm PRAL Inst, of Phys., London, UK, 27.6.84

Biersack, J.P.: Physical Concepts used In the TRIM Program University of Surrey, Guildford, UK, 26.6.84

Blersack, J.P.: Physical Principals In Atomic Collision Processes Naval Research Lab. Washington, Washington, USA, 31.7.84

Biersack, J.P.: Recent Developments and Results of the Monte-Carlo Program TRIM Naval Surface Weapons Center, Silver Springs, USA, 1.8.84

Biersack, J.P.: Recent Developments In Ion Stopping and Range Theory Solid State Division, ORNL, Oak Ridge, Tenn., USA, 6.8.84

Dauben, P. und Wahl, R.P.: Versetzungsringblldung In Cu+-lonenbestrahlten CuNl Legierungen bei 700 K FrühJahrstagung Deutsche Physikalische Gesellschaft, Freudenstadt, 22.3.83

- 133 -

Deglscher, H.P., Strecker, H. and Wagner, W.: Imaging Weak Coherency Strains In CuCo, AlZr and Nlmonlc PE16 Alloys 8th European Congress on Electron Microscopy, Budapest, Hungary, 15.8.84

Deglscher, H.P., Hein, W., Lacom, W., Strecker, H. and Wahl R.P.: Y'-Ausscheidung In der Nickelbasislegierung Nlmonlc PE16 Tagung der österreichischen Physikalischen Gesellschaft, Leoben, Austria, 26.-28.9.84

Fink, D., Biersack, J.P., Jshnel, F. und Hankslmann, R.: Untersuchung von Hellua, Lithium und Bor In Metallen alt Hilfe von (n,p>-und (n,a)-Reaktlonen Int. Conf. on the Analysis of Non-Metals In Metals, Berlin, 11.6.80

Fink, D., Blersack, J.P., Lauch, J., Jahne1, F., Müller, K. und Henkelmann, R.: BestloBung von Gitterpositionen In Lithiua und Bor mit Hilfe von (n,a)-Rcaktlonen alt thermischen Neutronen Arbeltstreffen des BMFT, Universität Konstanz, 30.9.80

Fink, D., Blersack, J.P., Osel, A.J., Jatrael, F., Müller, K., Henkelmann, R. and Caratanjen, H.D.: Studies on the Lattice Position of Boron In Silicon Vth Int. Conf. on Ion Beam Analysis, Sydney, Australia, 16.2.81

Fink, D.: The (n,p)- and (n,a)-Spectrometry Australian Atomic Energy Commission, Lucas Heights, Australia, 27.2.81

Fink, D.: Measurements on 'He in Metals by Means of (n,p)-Spectrometry Inst, of Nuclear Energy Research, Lung-Tan, Taiwan, 20.3.81

Fink, D.: Studies of B in Semiconductors by Means of (n,a)-Spectrometry Nuclear Engineering Division, Tsln Hua university, Chungli, Taiwan, 22.3.81

Fink, D.: Analysis of He, LI and B by Nuclear Reaction Techniques Material Science Division, Tsln Hua university, Chungll, Taiwan, 26.3.81

Fink, D.: Applications of (n,p)- and (n,a^Spectrometry Physics Dept., Tokyo University, Japan, 27.3.81

Fink, D.: Range and Damage Profiles of Light Nuclei implanted into Metals Dept. of Nuclear Engineering, Tohoku University, Sendal, Japan, 9.4.81

Fink, D.: The Thermal Behaviour of He implanted into Metals Dept. of Nuclear Engineering, Tohoku University, Sendai, Japan, 10.4.81

Fink, D.: Examlniation of He in Fusion Reactor Materials by Means of (n,p)- Spectro­metry Japan Atomic Energy Research Inst-, Tokal-mura, Japan, 12.4.81

- 134 -

Fink, D.: Depth Profile Determination and Lattice Location of Boron In Silicon Hitachi Central Research Lab., Tokyo, Japan, 16.4.81

Fink, D. and Blersack, J.P.: Catastrophic Sputtering of Sulfur Int. Conf. on Radiation Effecte In Insulators, Arco dl Gerda, Italy, 30.6.81

Fink, D., Blersack, J.P., Tjan, K., Jahnel, F. and Cheng V.K.: Range Profiles of Ha and Li in Solids 9th Int. Conf. on Atomic Collision in Solida, Lyon, France, 6.7.81

Fink, D. and Blersack, J.P.: The Background and its Reduction In (n,p)- and (n,a)-Spectrometry IVth Int. Conf. on Ion Implantation, Berchteagaden, 15.9.82

Fink, D., Blersack, J.P., Tjan, K., Henkelmann, R. and Jahnel, F.: Untersuchung leichter Elemente In Festkörpern mit Hilfe der (n,p)- und (n.a)-Spektrometrie Verbundtreffen "Komplementiere Methoden und Defekte", Harburg, 5.1--82

Fink, D., Blersack, J.P., Tjan, K., Cheng, V.K., Henkelaann, R. and Jahnel, F.: Reichweitenverteilungen und Diffusionsverhalten von Helium und Lithium in Festkärpern Verbundtreffen "Komplementiere Methoden und Defekte", Harburg, 6.10.82

Fink, D. and Blersack, J.P.: Isochrone Ausheizversuche an helluadotierten Metallen und Halbleitern FrühJahrstagung'der Deutschen Physikalischen Gesellschaft, Freudenstadt , 22.3.83

Fink, D.: Li, B und H in Ancient Materials 6th Int. Conf. on Ion Beam Analysis, Tempe, Ariz., USA, 25.5.83

Fink, D., Blersack, J.P., Staäele, H., Tjan, K. and Cheng, V.K.: Nitrogen Depth Profiling using the 14-N(n,p)14-C Reaction 6th Int. Conf. on Ion Beam Analysis, Tempe, Ariz., USA, 26.5.83

Fink, D., Bleraack, J.P., StXdele, M., Tjan, K. and Cheng, V.K.: Z2~Stopping Power Oscillations as derived from Range Measurements 6th Int. Conf. on Ion Beam Analysis, Tempe, Ariz., USA, 26.5.83

Fink, D., Bleraack, J.P., StXdele, M., Tjan, K., Haring, R.A. and de Vries, A.E.: Experiments on Sputtering of Group IV Elements 2nd Int. Conf. on Radiation Effects In Insulators, Albuquerque, USA, 31.5.83

Fink, D.: The (n,p)- and (n.a)-Spectrometry at the ILL Grenoble Inst. Laue-Langevin, Grenoble, France, 14.12.83

Fink, D., Biersack, J.P., StXdele, H., Carstanjen, H.D. and Behar, H.: Complementary Uses of Nuclear Reaction Analysis and Conventional Ion Beam Analysis Int. Workshop on New Uses of Ion Accelerators, Legnaro, Padua, Italy, 30.5.84

- 135 -

Fink, D., Biersack, J.P., Chen, J.T., Stadele, M. and TJan, K.: Implementation Profiles In Polymers MRS Meeting, Strasburg, France, 6.6.SA

Fink, D.: Series of 11 lectures at the UFRGS, Porto Alagre, Brazil, 16.7.-28.9.84

Gulling, H.-W., Poerachke, R., Wollenberger, H. und Schwahn, D.: Untersuchungen zur Hah- und Fernentmischung von CuNIFe Legierungen alt der Method« dar Neutronenbeugung FrühJahrstagung der Deutschen Physikalischen Gesellschaft, Münster, 2.4.82

Gudladt, H.-J., Macht, M.-P. und Naundorf, V.: Dlrakte Mesaung der Diffusion von Nl in Cu unter Bestrahlung Frühjahrstagung der Deutschen Physikalischen Gesellschaft, Münster, 9.3.81

Gudladt, H.-J., Macht, M.-P. und Naundorf, V.: Untersuchung der strahlungslnduzlerten Diffusion an verdünnten Cu-Legierungen FrühJahrstagung der Deutschen Physikalischen Gesellschaft, MUnster, 2.4.82

Gudladt, H.-J., Macht, M.-P. und Naundorf, V.: Strahlungslnduzlerte Diffusion In verdünnten Cu-Leglerungen FrühJahrstagung der Deutschen Physikalischen Gesellschaft, Freudenstadt, 22.1.83

Gudladt, H.-J.: Messung von partiellen Diffusionskoeffizienten In bestrahlten Legierungen Technische Universität Berlin, 1.7.83

Jahn, G.: Thermische Probiene in Vakuum Fortblldungsveranstaltung des HMI "Vakuumtechnik", 1.10.81

Koch, R. und Wahl, R.P.: GefügelnstabllitHt in CuBe Legierungen unter Selbstionenbestrahlung FrühJahrstagung der Deutschen Physikalischen Gesellschaft, Münster, 11.3.81

Koch, R., Wahl, R.P. und Wollenberger, H.: TEM-Untersuchungen an selbstionenbestrahlten CuBe FrUhJahratagung der Deutschen Physikalischen Gesellschaft, Münster 2.4.82

Krishan, K. and Abromeit, C.: Radiation Induced Instability in Concentrated Alloys Frühjahrstagung der Deuschen Physikalischen Gesellschaft, Freudenatadt, 24.3.83

Lang, R., Piller, J. und Wollenberger, H.: Untersuchung von Karbidausscheidungen In ferritlsche/martensitlschen Cr-Ti-C-Stühlen alt FIM und Atoaaonde Deutsche Gesellschaft für Metallkunde-Hauptversammlung, Aachen, 13.6.84

Macht, M.-P. Naundorf, V. and Wollenberger, H.: Diffusion of Alloy Components under Simulation Irradiation Second Topical Meeting on Fusion Reactor Materials, Seattle, USA, 10.8.81

- 136 -

Macht, M.-P.: A Method of Highly Sensitive Measurements of Thermal and Irradiation Induced Diffusion Coefficients Materials Science Division, Argonne National Lab., Argonne, USA, 1.9.81

Macht, M.-P., Naundorf, V. and DShl, R.: Measurement of Snail Diffusion Coefficients with SIMS DIMETA 1982 - Diffusion In Metals and Alloys, Tihany, Hungary, 1.9.82

Mertens, P. und Krist, Th.: The Energy Loss of 300 VceV He + and N"1" in 150 to 800 A Carbon Foils 9th Int. Conf. on Atomic Collisions in Solids, Lyon, France, 6.7.81

Mertens, P. und Krist, Th.: Electronic Stopping Cross Sections for 30-300 keV Protons in Materials with 23 < Z 2 < 30 9th Int. Conf. on Atomic Collisions in Solids, Lyon, France, 8.7.81

Mertens, P. und Krist, Th.: Stopping Ratios for 30-300 keV Ions with 1 < Z^ < 5 9th Int. Conf. on Atomic Collisions In Solids, Lyon, France, 8.7.81

Mertens, P.: Energy Loss of Low Energy Heavy Ions Solid State Science Branch, AECL Chalk River, Canada, 9.9.81

Mertens, P.: Measurements of Electronic Stopping Cross Sections for Low Energy Ions Nuclear Physics Journal Club, Queen's university, Kingston, Cansda, 29.9.81

Mertens, P.: Measurements of Electronic Stopping Powers for 30-300 keV Light Ions Memorial University of Newfoundland, St. John's, Canada, 5.10.81

Mertens, P. and Krist, Th.: Proton Energy at the Maximum of the Electronic Stopping Cross Section in Materials with 57 < Z 2 < 83 6th Int. Conf. on Ion Beam Analysis, Temp«, Ariz., DSA, 23.5.83

Mertens, P. and Krist, Th.: Stopping Ratios for 30-330 keV Ught Ions In Materials with 57 < Z 2 < 83 6th Int. Conf. on Ion Beam Analysis, Temp«, Ariz., OSA, 26.5.83

Mertens, P. and Krist, Th.: Application of Brandt's Effactive Charge Theory to Measurements for 50-350 keV Ions with 1 < Z L < 5 10th Int. Conf. on Atomic Collisions in Solids, Bad Iburg, 18.7.83

Mertens, P., Krist, Th. and Biersack, J.P.: The Nuclear Contribution to the Total Energy Loss of 300 keV Ions In Foils: a Comparison between Experiments and a TRIM-Calculatlon 10th Int. Conf. on Atomic Collisions in Solids, Bad Iburg, 21.7.83

- 137 -

Hertens, P.: Special Aspects of Energy Loss Measurements with 50-350 keV Light Ions tlniversitS de Lyon, Inst, de Physique nuclealre, Lyon, France, 12.9.83

Hertens, P.: Development of a Field Ion Microscope with Aton Probe Colloque franco-allcmande, Carry-le-Rouet, France, 17.9.83

Hertens, P.: FIH-Analysis of Decomposed CuNiFe-Alloys Colloque franco-allemande, Carry-le-Rouet, France, 17.9.83

Hertens, P.: Energieverlustmessungen an dünnen Folien Universität Linz, Linz, Austria, 27.6.84

Naundorf, V., Macht, M.-P., Gudladt, R.-J. and Wollenberger, H.: Measurement of Radiation Induced Impurity Diffusion in Copper Yamada Conf. on Point Defects and Defect Interactions in Metals, Kyoto, Japan, 16.11.81

Naundorf, V.: Untersuchung der strahlungainduzierten Fremdatomdiffusion mittels SIMS Inst, für Festkörperforschung der KFA Jülich, 23.11.82

Naundorf, V., Macht, H.-P., Wahl, R.P. and Wollenberger, H.: Bestimmung wesentlicher ElnfluBparameter der strahlungsinduzierten Ent­mischung und Ausscheidung Deutsche Gesellschaft für Hetallkunde-Hauptversamalung, Erlangen, 26.5.83

Naundorf, V., Macht, M.-P., Gudladt, H.-J., Koch, R., Wahl, R.P; and Wollenberger, H.: Radiation Induced Solute Diffusion and Segregation 26eme Colloque de Metallurgie I.N.S.T.N., Saclay, France, 21.6.83

Patil, R.V.: Anomalous Diffusion in Zirconium Based Alloys Frühjahrstagung der Deutschen Physikalischen Gesellschaft, Freudenstadt, 24.3.83

Patil, R.V., Naundorf, V., Macht, H.-P. and Wollenberger, H.: Direct Measurement; of Diffusion under Irradiation with Secondary Ion Mass Spectroscopy Syap. on Radiation Effects in Solids, Bhabha Atomic Research Centre, Bombay, India, 24.11.83

Piller, J.: Keimbildung und Wachstum von TiC-Ausscheidungen in a-Fe und der Einfluß von Sb-Zn-Leglerung Frühjahrstagung der Deutschen Physikalischen Gesellschaft Freudenstadt, 24.3.83

- 138 -

Piller, J., Mertens, P., Poerschke, R., Stajer, J-, Wagner, W., Wahl, R.P. und Wollenbarger, H.: Morphologie und quantitative Analyse der Mikrostruktur In entmischten CuNlFe Legierungen Früh Jahrstagung der Deutschen Physikalischen Gesellschaft, Munster, 14.3.84

Poerschke, R., Wagner, W. and Wollenberger, H.: Long-Range Atomic Clustering in Electron Irradiated NICu Alloys Vth Int. Conf. on Small Angle Scattering, Berlin, 8.10.80

Poerschke, R., Gulling, H.-W., Frlsius, D., Ibel, K. und Schwann, D.: Clustering ana Decomposition in Electron Irradiated CuNlFe Alloys Neutron Scattering Seminar, ECN Fetten, Petten, Netherlands, 18.11.80

Poerschke, R., Wagner, W. and Wollenberger, H.: Radiation Induced Interdiffusion and Phase Transformation in Electron Irra­diated CuNi Alloys Yamada Conf. on Point Defects and Defect Interactions in Metals, Kyoto, Japan, 20.11.81

Poerschke, R., GSlling, H.-W., Schwahn, D. and Wollenberger, H.: Diffuse and Small Angle Neutron Scattering Studies of Clustering and Decom­position in Electron Irradiated CuNiFe Alloys Advanced Study Inst, on Modulated Structure Materials, Crete, Greece, 24.6.83

Poerschke, R., Galling, H.-W., Schwahn, D. and Wollenberger, H.: Diffuse and Small Angle Neutron Scattering Studies of Clustering and Decom­position in Electron Irradiated CuNlFe Alloys Int. Conf. on Phase Transformation in Solids, Maleme-Chania, Crete, Greece, 26.6.83

Poerschke, R.: Strahlungsinduxlerte Diffusion und Nahordnung bzw. Nahentmischung in Legierungen Inst, für Festkörperphysik, der Universität Wien, Vienna, Austria, 3.10.83

Poerschke, R. and Schwahn, D.: Radiation Enhanced Diffusion as a Tool for Alloy Decomposition Studien at Low Temperatures: Neutron Scattering on Electron Irradiated CuNl Alloys Int. Conf. on Early Stages of Decomposition in Alloys, St. Andreasberg, 21.9.83

Poerschke, R., Gulling, H.-W., Wagner, W. and Wollenberger, H.: Radiation Induced Decomposition in CuNlFe Alloys Conf. on Phase Stability and Phase Traasformation«, BARC, Bombay, India, 8.2.84

Poerschke, R.: Neutron Scattering at the HMI, e.g. Study on the Decomposition in Alloys Phys. Dept. and Met. Dept. BARC, Bombay, India, 9.2.84

- 139 -

Foerschke, R.: Radiation Enhanced Diffusion and Decomposition In CuNl and CuNiFe Alloys Met. Dept. RRC, Kalpakkam, India, 14.2.84

Foerschke, R.: Short Range Clustering and Decomposition In Electron Irradiated CuNi and CuNiF« Alloys Indian Inst, of Science, Dept. of Solid State Chemistry and Metallurgy Dept., Bangalore, India, 15.2.64

Poei.*schke, R.: Decomposition in CuNiFe Alloys under Electron Irradiation Defence Metallurgy Research Laboratory, Hyderabad, India, 17.2.84

Foerschke, R.: Radiation Enhanced Diffusion and Phase Transformation in Electron Irradiated CuNi and CuNiFe Alloys Banaras Hindu University, Varanasl, India, 20.2.84

Poerschke, R.: A Comparative Study of the Decomposition in CuNiFe Alloys by Small Angle Neutron Scattering, Transmission Electron Microscopy and Atom-Probe-Field Ion Microscopy Banaras Hindu University, India, 21.2.84

Foerschke, R.: Short Range Clustering and Decomposition in Electron Irradiated CuNl and CuNiFe Alloys Roorkee university, India, 24.2.84

Foerschke, R., Hertens, F., PI Her, J., Wagner, W., Wahl, R.P. und Wollenberger, It.: Untersuchung der Entmischung von CuNlFe Legierungen mit Hilfe der Neutronenkleinwinkelstreuung Frühjahrstagung der Deutschen Physikalischen Gesellschaft , Münster 1984, 14.3.84

Poerschke, R.: Quantitative Messung der Nah- und Fernentmischung In CuNi und CuNiFe Legierungen nach Wärmebehandlung und Bestrahlung mit MeV-Elektronen Deutsche Gesellschaft für Metallkunde-Hauptversammlung, Aachen, 15.6.84

Strecker, H., Degischer, H.P., Hein, W., Wagner, W., Wahl, R.P. und Wollen­berger, H.: Neue Ergebnisse zur Gefügeentwicklung in Nlnonlc PE16 Deutsche Gesellschaft für Metallkunde-Hauptversammlung, Aachen 14.6.84

Strecker, H., Degischer, H.P., Wahl, R.P. und Wollenberger, H.: Determination of Size Distribution and Volume Fraction for y'-Precipitates In Nlmonlc PE16 by TEM 8th European Cong, on Electron Microscopy, Budapest, Hungary, 15.8.84

- 140 -

Wagner, W., Rehn, L.E. und Wiedersich, H.: Oberflitchenentmischung In der geordneten Phase NI3SI unter Bestrahlung FrUhjahratagung der Deutschen Physikalischen Gesellschaft, Münster, 2.4.82

Wagner, W., Rehn, L.E. und Wlederslch, H.: Strahlungslnduzierte Entmischung In konzentrierten NICu Legierungen Frithjahrstagung der Deutschen Physikalischen Gesellschaft, HUnster, 2.4.82

Wagner, W., Naundorf, V., Rehn, L.E. und Wlederslch, H.: Surface Segregation in Concentrated HiCu Alloys under Irradiation llth Int. Symp. on the 'Effects of Radiation on Materials', Scottsdale, USA, 29.6.82

Wagner, W.: Radiation-Induced Segregation in CuNi Alloys Materials Science Division, Argonne National Laboratory, Argonne, USA, 8.7.82

Wagner, W.: Experimente und Modellrechnungen zur strahlungsinduzierten Entmischung in konzentrierten NICu Legierungen GKSS, Geesthacht, 13.1.83

Wagner, W., Naundorf, V., Rehn, L.E. und Wlederslch, H.: Quantitative Analyse der strahlungsinduzierten Segregation in konzentrierten NiCu Legierungen Frühjahrstagung der Deutschen Physikalischen Gesellschaft, Freudenstadt, 23.3.83

Wagner, W.: The Neutron Süll Angle Camera Project in Berlin ILL Grenoble, Grenoble, France, 28.3.83

Wagner, W.: Decomposition in CuNiFe Alloys Investigated by Atomprobe FIM, Neutron Scat­tering and TEM Int. Conf. on Early Stages of Decomposition in Alloys, St. Andreasberg, 23.9.83

Wagner, W., Degischer, H.P., Piller, J. und Wollehberger, H.: Vergleichende Untersuchung der frühen Entaischungsstadien in Cu-2 At.Z Co mit FIM, TEM und Neutronen-KWS Frühjahrstagung der Deutschen Physikalischen Gesellschaft, Münster, IC.3.84

Wagner, W.: Neutronenleiter und Instrumentierung am ausgebauten BER II Inst, für FestkSrperforschung der KFA Jülich, 2.4.84.

Wahl, R.P.: Radiation-Induced Precipitation in Undersaturated CuBe Alloys Materials Science Division, Argonne National Laboratory, Argonne, USA, 31.7.81

- 141 -

Wahl, R.P., Koch, R. and Wollenberger, H.: TEM-Investigation of the Mlcrostructural Evolution In Simulation-Irradiated CuB* Alloy* Second Topical Meeting on Fusion Reactor Materials, Seattle, USA, 10.8.81

Wahl, R.P.: Influence of 300 k«V Self-Ion Irradiation on the Mlcrostructural Stability of a CuB« Alloy Dept. of Materials Science and Engineering, Cornell University, Ithaca, USA, 17.8.81

Wahl, K.P.: Phase Change in Alloys through Irradiation: A TEM-Study on CuBe Alloys

. US Steel Research Laboratory, Monroeville, USA, 18.8.81 Wahl, K.P., Koch, R. und Wollenberger, R.:

CefilgeinstabilitiCt einer CuBe Legierung unter Schwerionenbestrahlung: Eine TEM-Untersuchung Deutsch* Gesellschaft für Metallkunde-Hauptversammlung, Vlllach, Austria, 3.6.82

Wahl, R.P., Koch, R. and Wollenberger, H.: Formation of Precipitates under Irradiation in an Undersaturated CuBe Alloy EMAG '83, University of Surrey, Guildford, UK, 1.9.83

Wahl, R.P.: TEM-Untersuchung und Entmischungskinetik und Morphologie einer CuNiFe Legierung 21. Tagung der Deutschen Gesellschaft für Elektronenmikroskopie, Antwerpen, Belgium, 19.9.83

Wahl, R.P., Macht, M.-P., Naundorf, V. and Wollenberger, H.: Investigation of Chemical Redistribution in Dilute Cu-Alloys under Simula­tion Irradiation Third Topical Meeting on Fusion Reactor Materials, Alburquerque, New Mexico, USA, 21.9.83

Wahl, R.P.: Diffusion und Ausscheidungskinetik in CuBe unter Bestrahlung Friihjahrstagung der Deutschen Physikalischen Gesellschaft, Münster, 12.3.84

Wahl, R.P.: Gefüge-Entwicklung in einer ungesättigten CuBe Legierung unter Selbstionen­bestrahlung Inst, für Festkörperforschung, KFA Jülich, 3.4.84

Wollenberger, H.: Diffusion und Phasenumwandlung unter dem Einfluß von Bestrahlung Institut für Metallforschung d. Kernforschungszentrum Karlsruhe, 21.11.80

Wollenberger, H.: Metallische Werkstoffe Im nuklearen Strahlungsfeld Inst, für Allgem. Metallk. und Metallp!/bik der RWTH Aachen, 6.12.80

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Wollenberger, H.: Measurement of Radiation-Induced Diffusion Coefficients Metallurgy Division, Bhabha Atomic Research Centre, Bombay, India, 23.3.81

Wollenberger, H.: Short Range and Longe Range Clustering in Irradiated CuNi Alloys Metallurgy Division, Bhabha Atoalc Research Centre, Bombay, India, 25.3.81

Wollenberger, H.: Radiation-Induced Segregation in CuBe Alloys Metallurgy Division, Bhabha Atomic Research Centre, Bombay, India, 27.3.81

Wollenberger, H.: Diffusion and Segregation in Irradiated Alloys Materials Science Laboratory, Reactor Research Centre, Kalpakkam, India, 30.3.81

Wollenberger, H.: Diffusion and Segregation in Irradiated Alloys Indian Institute of Technology, Madr&t, India, 6.4.81

Wollenberger, H.: Diffusion and Segregation in Irradiated Alloys Indian Institute of Technology, Bangalore, India, 8.4.81

Wollenberger, H.: Messung von partiellen Diffusionskoeffizienten in Legierungen bei Simulationsbestrahlung Second National Conf. on Fusion Reactor Materials, Dubna, USSR, 22.4.81

Wollenberger, H.: Recent Results of Irradiation-Induced Diffusion Coefficient Measurements Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, USA, 6.8.81

Wollenberger, H.: Entwicklung des Mikrogeftiges metallischer Werkstoffe unter Bestrahlung Inst, für Reaktorwerkstoffe der Kernf orschungsan.1 age Jülich, 3.11.81

Wollenberger, H.: Interstitialcy Transport In Dilute Alloys under Irradiation Yamada Conf. on Point Defects and Defect Interactions in Metals, Kyoto, Japan, 18.11.81

Wollenberger, H.: Fhasenumwandlung unCer nuklearer Bestrahlung Ferienkurs "Physikalische Grundlagen metallischer Werkstoffe", Jülich, 5.3.82

Wollenberger, H.: S trahlungsinduzierte Phasenumwandlungen Frühjahrstagung der Deutschen Physikalischen Gesellschaft, Münster, 2.4.82

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Wollenberger, H.: Mobile and Immobile Solute-Interstitial Complex?' Cordon Research Conf. on Physical Metallurgy, Proctor Academy, Andover, USA, 14.7.82

Wollenberger, H.: Partial Diffusion Coefficient Measurements In Irradiated Materials Dept. of Nucl. Energy, University of Wisconsin, Madison, USA, 19.7.82

Wollenbergar, R.: Irradiation-Induced Solute Segregation Materials Science Division, Argonne National Laboratory, Argonne, USA, 22.7.82

Wollenberger, H.: Irradiation-Driven Phase Changes in Alloys Brookhaven National Laboratory, Brookhaven, USA, 23.7.82

Wollenberger, H., Gudladt, H.-J., Koch, R., Macht, M.-P., Naundorf, V. and Wahl, R.P.: Be Diffusion Coefficient and Y-Preclpitation Growth Rate in Self Ion Irra­diated Dilute CuBe Alloys BNES Conf. on Dimensional Stability and Mechanical Behaviour of Irradiated Metals and Alloys, Brighton, UK, 12.4.83

Wollenberger, H. und Abromeit, C : Mechanismen strahlungslnduzierter Phasenumwandlung Deutsche Gesellschaft für Metallkunde-Hauptversammlung, Erlangen, 27.5.83

Wollenberger, H.: Kinetics of the Alloy Decomposition in the System CuNlFe Centre d'Etudes NuclSaires de Fontenay aux Roses, France, Section d'Etudes des Solides IrradiSs, Seminaire de Metallurgie Physique, 27.11.83

Wollenberger, H.: Interstitial-Solute Interaction in Copper Centre d'Etudes Nucleaires de Saclay, Section de Recherches de Metallurgie Physique, Gif-sur-Yvette, France, 2.2.84

Wollenberger, H.: Diffusion Coefficient Measurements In Self-Ion Irradiated Dilute Alloys Centre d'Etudes Nuclgalres de Saclay, Section de Recherches de Metallurgie Physique, Gif-sur-Yvette, France, 9.2.84

Wollenberger, H.: Irradiation Induced Y-Precipltation in an Undersaturated CuEä Alloy Centre d'Etudes NuclCaires de Saclay, Section de Recherches de Metallurgie Physique, Gif-sur-Yvette, France, 16.2.84

Wollenberger, H.: Irradiation Influence on the Alloy Decomposition of CuNl and CuNiFe Centre d'Etudes Nucleaires de Saclay, Section de Recherches de Metallurgie Physique, Gif-sur-Yvette, France, 8.3.84

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Wollenberger, H.: Kinetics of the Alloy Dacoaposltlon in CuNiFe UniversitC de Rouen, Section de Physique, France, 16.3.84

Wollenberger, H.: Radiation Induced Diffusion and Phase Transformation Studies in the Hahn-Meitner-Institute Berlin Centre d'Etudea Nucleairee Grenoble, Department de Recherche Fondaaentale, Grenoble France, 17.3.84

Wollenberger, H.: Forachung und Entwicklung auf den Wege zur wirtschaftlichen Nutzung der Kernfusion Berliner Wissenschaftliche Gesellschaft, Berlin, 17.5.84

Wollenberger, H.: Ausscheidungskinetik bei nahentaischtem Ausgangszustand Deutsche Gesellschaft für Metallkunde-Hauptversammlung, Aachen, 15.6.84

Wollenberger, H.: Neutron Small Angle Scattering, Field Ion Microscopy and Atomprobing of Unmixing Alloys Met. and Mat. Eng. Dept. University of Pittsburgh, Pittsburgh, USA, 21.6.84

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UNIVERSITY LECTURES

Biersack, J.F.: Freie Universität Berlin Fachbereich Physik Institut für Kernphysik

Felix, F.W.: Technische Universität Berlin Fachbereich Physikalische und Angewandte Chemie Fachbereich Kernchemie

Wollenberger, H.: Technische Universität Berlin Fachbereich Werkstoffwissenschaften Institut für Hetallforschung

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VI. COOPERATIONS

JOINT PROGRAMS:

Association contract with the KFA Jülich for research of fusion reactor tech­nology within the association contract between the KFA Jülich and EURATOM.

Cooperation prograa "Diffusion and Phase Stability In Irradiated Alloys" with BARC Bombay and the RRC Kalpakkan, Indo-FRG Bilateral Agreement for Cooperation In the Peaceful Uses of Atomic Energy.

Cooperation project "Development of experimentally founded calculation models to optimize materials and structural parts under cyclic load at elevated tem­peratures" with the Bundesanstalt für Materialprüfung Berlin and the Institut für Metallforschung der Technischen Universität Berlin.

COOPERATIONS WITH OTHER INSTITUTES:

1. Institut für Radiochemie der Technischen Universität München, D-8046 Garchlng 2. Ratgen-Labor der Staatlichen Museen Preusslscher Kulturbesitz, D-1000 Berlin 30 3. Institut für nichtmetallische und keramische Werkstjffe, Technische

Universität Berlin, D-1000 Berlin 12 4. Sonderforschungsbereich 125, "Fehlordnung In Metallen", Aachen-Jülich-Köln,

D-5100 Aachen 5. Hahn GmbH Industrieplanung, Bismarckatr. 16, D-1000 Berlin 41 6. Institute of Nuclear Energy Research, Lung-Tan, Taiwan, China 7. Sektion Physik der Technischen Universität München, D-8000 München 8. Institut für Festkörperforschung der KFA Jülich GmbH, D-5170 Jülich 9. Fachbareich Elektrotechnik, Hochschule der Bundeswehr München, D-8000 München 10. Institute of Physics of the University of Zagreb , Zagreb, Yugoslavia 11. Institut für Physik der GKSS Geesthacht, D-2054 Geesthacht-Tesperhude 12. IBM Research, Torktown Heights, New York 10598, USA 13. AERE Barwell, Oxfordshire 0X11 ORA, UK 14. Plasma-Wand-Wechselwirkung, Max-Planck-Institut für Plasmaphysik, D-8046 Garchlng, 15. Institut für Physik, Max-Planck-Institut für Metallfor&chung, D-7000 Stuttgart 80 16. Institut für Festkb'rpertechnologle, D-8000 München-Pasing 17. technoflex GmbH, Kanstr. 54, D-1000 Berlin 12 18. Centro Atfimlco Bariloche, Bariloche, Argentina 19. Materials Science Div., Reactor Research Centre Kalpakkam, Tamil Nadu, India 20. Materials Science Branch, Chalk River Nucl. Labs, Chalk River, Ontario

KOJ 1J0, Canada 21. Materials Science and Technology, Argonne National Lab., Argonne, II. 60439, USA 22. Physical Metallurgy Div'., Bhabha Atomic Research Centre, Bombay, India 23. Inst. f. Festkörperphysik der Universität Wien, Vienna, Austria

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24. National Research Laboratory, Risrf, Denmark 25. Institut für Hetallforschung, Technische Universität Berlin, D-1000 Berlin 15 26. Inseltute Laue-Langevin, Grenoble, France 27. BBC Brown Boveri & Co Forschungszentrum, Dättwll, Switzerland 28. Österreichisches Forschungszentrua Seibertdorf QabH, Institut für

Werkstofftechnologic, Vienna, Austria 29. FOM-Institute voor Atooa-en Moleculfysica, Amsterdam, Netherlands 30. Institute of Physics, University of Catania, Catania, Italy 31. University of Lisbon, Lisbon, Portugal 32. Physikalisches Institut der Technischen Universität Basel, Basel, Switzerland 33. Instlt. Fisica, Universidad Federal Rio Grande do Sul, Porto Alegre, Brazil 34. Sandia Laboratories, Llvernore, USA

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VII. LEAVES TO FOREIGN INSTITUTES

Abromelt, C : Materials Science Laboratory, Reactor Research Center Kalpakkaa - 603102, Taall Nadu, India, 1.12.81 - 19.2.82

Materials Sclance Branch Chalk River Nucl. Labs., Chalk River, Ontario KOJ 1J0 Canada, 25.S.83 - 25.8.83

Biersack, J.P.: IBM, Watson Research Lab. Yorktown Heights, Hew York 10598, USA, 18.1.82 - 3.4.82

Unlversidad Federal Rio Grande do Sul, Forto Alegro, Brazil, 21.2.83 - 9.4.83

Institute of Semiconductors, Chinese Academy of Sciences Beijing, Peking, China, 12.10.83 - 7.11.83

Shanghai Institute of Metallurgy, Chinese Academy of Sciences, Shanghai, China

Royal Melbourne Institute of Technology, Melbourne, Australia, and CSIRO, Clayton, Australia, 7.11.83 - 7.12.83

Fink, D.: Universidad Federal Rio Grande do Sul, Porto Alegro, Brazil, 7.7.84 - 8.10.84

Hertens, P.: Queen's University, Kingston, Canada, 13.5.83 - 14.6.83

Wagner, W.: Materials Science Division, Argonne National Lab., Argonne, Illinois 60439, USA, 1.4.80 - 31.8.81

Institut Max von Laue - Paul Langevin, B. P. 156X, 38042 Grenoble Cedex, France, 21.4.82 - 19.6.82

Wollenberger, H.: Section de Recherche de Metallurgie Physique, CEA - Saclay, 91190 Gif-sur-Yvette, Saclay, Paris, France, 3.10.83 - 20.4.84

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VIII. GUEST RESEARCHERS

Anantharaman, T.R.: Departaant of Metallurgical Engineering, Banaras Hindu University, Varanasi, India, 1.3.81 - 31.7.81

Anantharaaan, T.R.: Institute of Technology, Banaras Hindu University, Varanasi, India, 1.7.83 - 31.8.83

Bolze, M.: Technisch* Unlversltüt MUnchen, D-8000 MUnchen, 18.4.83 - 22.4.83 and 14.5.84 - 19.5.84

Degischer, H.P.: Österreichisches Forschungszentrum Selbersdorf, Vienna, Austria, since 5.4.83

Ecker, K.H.: Materials Science Division, Argonne National Laboratory, Argonne, II., USA, 1.7.76 - 30.6.81

Huhne1, R.: Institut für Metallforschung, Technische Universität Berlin, D-1000 Berlin 15, 1.4.80 - 30.6.84

Hahn, H.: Institut fUr Metallforschung, Technische Universität Berlin, D-1000 Berlin 15, 1.9.78 - 30.6.82

Jakas, M.M.: Centro Atömlco Bariloche, Argentina, 12.6.83 - 12.8.83

Krishan, K.: Materials Science Laboratory, Reactor Research Centre, Kalpakkaa, India, 9.2.83 - 9.6.83

Lenarczyk, Z.J.: Ministerium für Arbelt und Sozialwesen, Warsaw, Poland, 1.1.80 - 31.8.81

Merkle, K.L.: Materials Science Division, Argonne National Laboratory, Argonne, II., USA, 3.1.30 - 30.6.80

Patil, R.V.: Metallurgy Division, Bhabha Atomic Research Centre, Trombay, Bombay, India, 1.8.82 - 4.11.83

Pfeiler, W.: Institut für Festkörperphysik der Universität Wien, Vienna, Austria, 12.12.83 - 16.12.83

Rauch, K.: Technisch* Universität MUnchen, D-8000 München, 18.4.83 - 22.4.83 and 14.5.84 - 19.5.84

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Stajer, J.Z.: Hinlsteriua für Arbelt und Sozialwesen, Warsaw, Poland, 16.6.82 - 15.6.84

van Dljk, C.: ECN Fetten, Fetten, The Netherlands, 9.1.84 - 20.1.84

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IX. STAFF

Head Secretary

Scientific Staff

Abromeit, Christian Biersack, Jochen Feter Dauben, Feter* Felix, Fred W. Fink, Dietmar Hein, Wilfried* Kell, Burkhard* Koch, Annette** Kriat, Thomas Krüger, Wolfgang Lang, Roland** Macht, Michael-Peter Hertens, Feter Miekeley, Wolfgang Mittler, Alfred* Müller, Manfred Naundorf, Volkaar Foerschke, Rainer Scheuer, Udo* Strecker, Harald Tenbrlnk, Johannes* Tjan, Kle* Wagner, Werner Wahl, Rajeshwar Praaad Zhu, Fengwu

Wollenberger, Heinrich Standkc, Barbara

Technical Staff

Borck, Klaus Dencks, Ingrid Friedrich, Günter Gadomski, Peter Hill, Michael Jahn, Gerwin Liste, Liane Michalskl, Nicole RSnnfeldt, Werner Tietze, Werner V81z, Peter-Rüdiger Weber, Sabine

* Doktorand ** Diplomand

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