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DISLOCATION RELAXATION PROCESSES IN METALS
P. Groh, H. Schultz
To cite this version:
P. Groh, H. Schultz. DISLOCATION RELAXATION PROCESSES IN METALS. Journal de Physique
Colloques, 1981, 42 (C5), pp.C5-25-C5-30. �10.1051/jphyscol:1981502�. �jpa-00220958�
JOURNAL DE PHYSIQUE
CoZZoque C5, suppZ6ment au nO1O, Tome 42, octobre 1981 page C5-25
DISLOCATION RELAXATION PROCESSES I N METALS
P. Groh and H. ~ c h u l t z *
Laboratoire de Physique des SoZides, associ6 au C.N.R.S., I.N.S.A., 31077 Toulouse Cedex, France
"!dux-~Zanck-~nstitut fur MetaZZforschung, Institut fur Physik, Heisenbergstr.1, 0-7000 Stuttgart 80, and Institut fiir Theoretische und Angewandte Physik der Universitat Stuttgart, F.R.G.
A b s t r a c t . - Original c o n t r i b u t i o n s on d i s l o c a t i o n r e l a x a t i o n e f f e c t s , submitted t o t h i s conference, a r e introduced. The c o n t r i b u t i o n s a r e concerned with i n t r i n s i c d i s l o c a t i o n r e l a x a t i o n e f f e c t s a s well a s with some d i s l o c a t i o n - point d e f e c t i n t e r a c t i o n s , e s p e c i a l l y hydrogen-disl ocation i n t e r a c t i o n . In f .c.c. metals, t h e kink-pair formation model f o r t h e Bordoni peaks obtained f u r t h e r support by new experiments. In b . c . c , metals, by experiments on high p u r i t y and hydrogen charged specimens considerable progress has been achieved i n t h e understanding of t h e mechanisms r e s p o n s i b l e f o r t h e numerous r e l a x a t i o n peaks: a general agreement i s obtained f o r t h e main i n t r i n s i c and hydrogen induced processes.
1. I n t r o d u c t i o n . - In t h i s paper we introduce o r i g i n a l contributions submitted t o t h i s conference, which a r e concerned with i n t r i n s i c d i s l o c a t i o n r e l a x a t i o n e f f e c t s a s well a s with some d i s l o c a t i o n - p o i n t d e f e c t i n t e r a c t i o n s . The o r i g i n a l c o n t r i b u t i o n s a r e quoted here with t h e names of t h e a u t h o r s , o t h e r references a r e given with numbers of a reference 1 i s t .
H i s t o r i c a l l y , i n f . c . c . metals a c l e a r s e p a r a t i o n i s we1 1 e s t a b l i s h e d between i n t r i n s i c d i s l o c a t i o n processes (Bordoni peaks) and d i s l o c a t i o n - p o i n t d e f e c t i n t e r - a c t i o n e f f e c t s . Mobile d i s l o c a t i o n segments may i n t e r a c t with point d e f e c t s which a r e i n t r i n s i c and mobile (Hasiguti peaks), e x t r i n s i c and mobile ( e . g . hydrogen dragging e f f e c t s o r more general Snoek-Koester peaks, o r immobile (unpinning peaks).
Such a c l a s s i f i c a t i o n scheme may be i n s u f f i c i e n t f o r an e x a c t d e f i n i t i o n of a mechanism, but i t may s e r v e a s a f i r s t guide.
A t t h i s conference a considerable number o f c o n t r i b u t i o n s i s concerned with b . c . c . metals. Here such a c l e a r s e p a r a t i o n of i n t r i n s i c d i s l o c a t i o n e f f e c t s i s p a r t l y a problem. Especially i n V , Nb, Ta i n t e r s t i t i a l s o l u t e atoms (H,O,N,C) a r e always p r e s e n t i n various concentration ranges (1-1000 atppm), and u l t r a - h i g h vacuum ( U H V ) techniques a r e required t o reduce t h e i n t e r s t i t i a l s o l u t e c o n t e n t . In Nb, Ta t h e o r d e r of 1 atppm i n t e r s t i t i a l s o l u t e concentration can be obtained. Even a t such a low level i n t e r a c t i o n e f f e c t s with d i s l o c a t i o n s may appear. For low temperatures t h e i n t e r a c t i o n with mobile H has t o be considered, f o r high temperatures (T>400 K) i n t e r a c t i o n s with mobile 0 ,
N,
C may become important.Therefore i t i s much more d i f f i c u l t i n b . c . c . metals t o d i s t i n g u i s h between i n - t r i n s i c d i s l o c a t i o n e f f e c t s and d i s l o c a t i o n - i m p u r i t y i n t e r a c t i o n s . UHV p u r i f i c a t i o n
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1981502
C5-26 JOURNAZ. DE PHYSIQUE
techniques l e t achieve considerable progress r e c e n t l y and t h e i n t r i n s i c d i s l o c a t i o n processes i n b.c.c. metals as w e l l as s t u d i e s on s p e c i f i c d i s l o c a t i o n - p o i n t d e f e c t i n t e r a c t i o n s has become a ~ a j o r t o p i c o f t h i s session.
I n t r i n s i c d i s l o c a t i o n r e l a x a t i o n e f f e c t s i n f.c.c. metals (Bordoni peaks) a r e p r e s e n t l y considered as f a i r l y w e l l understood [I]. This i s r e f l e c t e d i n a lower num- ber o f o r i g i n a l c o n t r i b u t i o n s t o t h i s t o p i c . However, t h e presented papers g i v e an- swer t o some i m p o r t a n t open questions. Generally speaking, we a r e i n a phase o f con- s o l i d a t i o n of t h e k i n k - p a i r formation model f o r t h e Bordoni peaks. I n v e s t i g a t i o n s a r e extended a l s o t o hexagonal nletals, which show s i m i l a r behaviour as f.c.c. metals.
A h i g h l i g h t o f our session c e r t a i n l y i s the p r e s e n t a t i o n o f r e s u l t s , obtained w i t h a new experimental technique, which can d e l i v e r d i r e c t l y i n f o r m a t i o n on the u n d e r l y i n g mechanism o f a r e l a x a t i o n e f f e c t (Gremaud, B e n o i t ) .
Some c o n t r i b u t i o n s a r e concerned w i t h extreme m a t e r i a l s . One paper deals w i t h s o l i d ~ e which e x i s t s under h i g h pressure a t u l t r a - l o w temperatures i n a b.c.c. ~ , s t r u c t u r e , where d i s l o c a t i o n e f f e c t s have been s t u d i e d (Iwasa, Saito, Suzuki). Less extrem, b u t s t i l l a challenge f o r t h e e x p e r i m e n t a l i s t a r e i n v e s t i g a t i o n s on a l k a l i metal s i n g l e c r y s t a l s , on which systematic s t u d i e s on d i s l o c a t i o n r e l a x a t i o n e f f e c t s have been presented (Hamnerschmid, Kirchner, Schoeck).
Several papers a r e concerned w i t h hydrogen-dislocation i n t e r a c t i o n s i n metals and a l l o y s o f d i f f e r e n t s t r u c t u r e , p a r t l y by techniques s e n s i t i v e t o s u r f a c e condi- t i o n s and w i t h q u i t e d i f f e r e n t i n t e n t i o n s .
We mention a l s o a paper on f a t i g u e i n Cu s t u d i e d by i n t e r n a l f r i c t i o n technique (Mi zubayachi
,
Okuda).
I n t h e remaininq p a r t o f t h i s paper we w i l l review some new r e s u l t obtained on b.c.c. and f . c . c . metals.
2. D i s l o c a t i o n r e l a x a t i o n peaks i n b.c.c. metals
2.1 Nomenclature.- Chambers [21 c a l l e d t h e peaks a,B,y i n the o r d e r o f i n c r e a s i n g temperature, where a and y were considered as i n t r i n s i c d i s l o c a t i o n r e l a x a t i o n peaks, B as due t o d i s l o c a t i o n - p o i n t d e f e c t i n t e r a c t i o n s . L a t e r a' was observed as a low temperature subpeak o f a.
The Grenoble group i n t r o d u c e d f u r t h e r
Pa
o rB
f o r i n d i c a t i n g i n t e r a c t i o n e f f e c t sY
between d i s l o c a t i o n segments mobile i n t h e a o r y regime r e s p e c t i v e l y and i n t e r a c t i n g w i t h i n t e r s t i t i a l s o l u t e atoms (H,O,N,C), and B1,
B2
f o r i n t e r a c t i o n processes w i t h i n t r i n s i c p o i n t defects.Three remarks should be added: (1) The a peak i n Ho (Grau, S c h u l t z ) , which can be s t u d i e d i n h i g h p u r i t y samples i n an convenient temperature regime, has been separated i n 4 subpeaks, c a l l e d al..a4 ( i n t h e o r d e r o f decreasing temperature), ( 2 ) I n V, Nb, Ta the peaks c a l l e d "a" i n the p a s t a r e due t o hydrogen decorated d i s - l o c a t i o n segments (see [ 3 ] , R i t c h i e ' s review; Maul, Schultz; Okuda, Mizubayashi e t a1 .).
( 3 ) R i t c h i e i n h i s review suggests t o preserve a' f o r geometrical k i n k m i g r a t i o n i n screw components (GKM(B)), and a f o r k i n k - p a i r formation i n non screws ( K P F ( 1 ) ) .
2 . 2 Low temperature d i s l o c a t i o n r e l a x a t i o n e f f e c t s i n b.c.c. metals.- D i s l o c a t i o n e f f e c t s f r e e from i n t e r f e r e n c e w i t h H s o l u t e atoms were s t u d i e d i n d e t a i l i n Fe and Mo. One observes i n both metals a complex a peak, i n Fe u s u a l l y 2 subpeaks a r e r e - ported, i n Mo t h e r e e x i s t d i s t i n g t l y more than 2, probably 4 subpeaks [ 4 ] . A process, r e l a t e d t o i n t r i n s i c p o i n t defects, appears i n Mo as a h i g h temperature shoulder o f a. The 6 process i n Fe shows an e v o l u t i o n and f i n a l l y a t r a n s f o r m a t i o n i n t o peak a i n t h e cours o f annealing [ 5 ] . The c h a r a c t e r i s t i c i n f l u e n c e o f annealing i n t h e tempera- t u r e regime o f stage 111 recovery ( p o i n t d e f e c t recovery) as r e p o r t e d i n [51 can be seen more o r l e s s c l e a r l y i n a l l b.c.c. metals, i n v e s t i g a t e d so f a r 163.
The
6
peaks a r e considered as t h e analogous t o t h e H a s i y t i peaks i n f . c . c . metals. They r e q u i r e the presence o f i n t r i n s i c atomic defects, however, 1 ess i s known f o r t h e 6 peaks. Here i s an open f i e l d f o r t h e f u t u r e . For an deeper understanding one has t o consider t h e m o b i l i t y o f p o i n t d e f e c t s i n b.c.c. metals. Below we g i v e t h e temperatures f o r t h e onset o f d e f e c t m o b i l i t y f o r some b.c.c. metals: Fe (125 K, 250 K), Mo ( 3 5 K/500 K), W (27 K/800 K), Nb (<8 K, 250 K), Ta (<8 K, 300 K). The inde- cated temperatures a r e recovery temperatures f o r p o i n t d e f e c t s created by i r r a d i a t i o n [ 7 ] . It should be noted t h a t i n terms o f a t w o - i n t e r s t i t i a l model i t i s expected t h a t p l a s t i c deformation creates o n l y i n t e r s t i t i a l atoms which become mobil a t h i g h e r temperatures, i n t h e so c a l l e d stage I 1 1 ( t h e h i g h e r temperature i n d i c a t e d above). Whereas i n a o n e - i n t e r s t i t i a l model deformation induced i n t e r s t i t i a l atoms should m i g r a t e a t the lower temperature, i n d i c a t e d above. The reader may n o t e t h a t d e f e c t m o b i l i t y i n Fe s t a r t s a t 125 K, i n Nb below 8 K. A c r i t i c a l examination o f t h e e v o l u t i o n o f t h e low temperature d i s l o c a t i o n i n t e r n a l f r i c t i o n peaks w i l l be i n t e r e s t i n g .We t u r n s h o r t l y t o t h e subpeaks o f a. I n Yo, a c t i v a t i o n parameters, e s p e c i a l l y a c t i v a t i o n volumes ( f o r d e t a i l s see [ 4 ] ) a r e compatible w i t h the f o l lo w i n g i n t e r p r e - t a t i o n : al-KPF (L), a3,aq-GKM ( 8 ) f o r two d i f f e r e n t geometrical kinks, e.g. K: and K: [81.
I n Fe two processes of a are separated. A general view s i m i l a r as i n Mo (GKM(0) and KPF
(I))
has been o b t a i n e d by AstiP, Peyrade, Groh. However, Yagalas, Moser, have n o t found support f o r a GKM component. Microdeformation r e s u l t s c o n f i r m i n Fe t h a t a main component o f ci i s due t o KPF(I)
(San Juan, No, Fantozzi, Esnouf, Vanoni).Magalas, Moser suggest t h a t d i s l o c a t i o n s w i t h d i f f e r e n t Burgers' v e c t o r s may be r e s - p o n s i b l e f o r the s u b s t r u c t u r e o f a.
I n V, Nb, Ta small amounts of hydrogen ( 2 1 atppm) c r e a t e H-Snoek-Koester peaks, which were c a l l e d "a peaks" i n t h e past, and which mask t h e i n t r i n s i c d i s l o c a t i o n r e - l a x a t i o n e f f e c t s . I t i s hoped t h a t t h e d e t a i l e d i n v e s t i g a t i o n ~ o f Maul e t a l . [ 3 ] on Nb w i t h c o n t r o l l e d amounts of H w i l l end a l o n g standing controversy concerning t h i s p o i n t . T h i s view i s confirmed by Okuda, Mizubayachi, Kuramochi e t a l .
.
S t i l l open i s a f i n a l understanding o f t h e combined a c t i o n o f H and 0 on the r e l a x a t i o n s t r e n g t h and t h e f i n e s t r u c t u r e o f the i n t e r a c t i o n peaks.C5-28 JOURNAL DE PHYSIQUE
2.3 H i g h t e m p e r a t u r e peaks i n b . c . c . m e t a l s . - There i s general agreement t o r e l a t e t h e y peak t o KPF (El), i . e . t o correspond t o t h e phenomenon c o n t r o l l i n g t h e l o w tem- p e r a t u r e p l a s t i c i t y o f b.c.c. p e t a l s . The y peak i s s t u d i e d i n Ta ( R o d r i a n , S c h u l t z ) , Mo (Grau, S c h u l t z ) , Nb (DeLima, B e n o i t ) , Fe ( A s t i $ , Peyrade, Groh) and p r e s e n t s v e r y c l o s e d c h a r a c t e r i s t i c s : i t s t e m p e r a t u r e i s near t h e knee t e m p e r a t u r e o f t h e f l o w s t r e s s - t e m p e r a t u r e curve, i t s w i d t h i s near t h e Debye w i d t h and i t shows a tendency t o anneal o u t q u i c k l y . I n Nb [ 9 1 and Fe
[ l o ]
t h e i n s t a b i l i t y o f t h e y peak i s s t u d i e d i n d e t a i l and i t i s shown t h a t i t i s connected w i t h t h e i n s t a b i l i t y o f t h e screw n e t - work. Long s t r a i g h t screw d i s l o c a t i o n s , as p r e s e n t a f t e r l o w t e m p e r a t u r e d e f o r m a t i o n , a r e expected t o bow o u t under t h e i n f l u e n c e o f i n t e r n a l s t r e s s e s , as soon as t h e tem- p e r a t u r e of t h e y peak i s reached. Thereby l o w e r i n g t h e l e n g t h o f screw components ( A s t i 6 e t a l . [ l o ] ) . Experiments on Mo [ 4 ] a r e a l s o i n l i n e w i t h t h e s e s u g g e s t i o n s and i n d i c a t e t h e r e d u c t i o n o f screw components as w e l l as o f i n t e r n a l s t r e s s e s i n t h e y regime. The s i t u a t i o n i n Ta[I11
i s more c o m p l i c a t e d . A t t h e peak t e m p e r a t u r e 0 s o l u t e atoms become m o b i l e a n d p i n n i n g e f f e c t s i n t e r f e r e w i t h changes o f t h e screw d i s - l o c a t i o n s t r u c t u r e . A subpeak, y2 i s s t a b l e i n t h e presence o f 0 s o l u t e atoms and R o d r i a n [ 9 1 g i v e s arguments t h a t y2 i s due t o GKM (0), where t h e k i n k s a r e d e c o r a t e d w i t h m o b i l oxygen atoms.A y peak can be observed a l s o i n K (Hammerschmid, K i r c h n e r , Schoeck) and t h e s e o b s e r v a t i o n s s u p p o r t t h e i d e a t h a t t h e s p e c i f i c p r o p e r t i e s of screw d i s l o c a t i o n s a r e of c r y s t a l l o g r a p h i c o r i g i n and n o t a phenomenon p r e s e r v e d t o t r a n s i t i o n m e t a l s .
Some r e s u l t s on t h e Snoek-Koester peak (SK peak) o f 0 o r C a r e presented. Here an e x a m i n a t i o n o f a r e c e n t t h e o r y by Seeger [ 1 2 ] i s o f i n t e r e s t . Up t o now t h e ex- p e r i m e n t a l r e s u l t s p r e s e n t e d a r e n o t d e t a i l e d enough t o g i v e a f i n a l e v a l u a t i o n . F o r Ta-0 (Rodrian, S c h u l t z ) agreement o r a t l e a s t c o n s i s t e n c y w i t h t h e t h e o r e t i c a l p r e - d i c t i o n s has been o b t a i n e d . F o r Fe-C, Magalas, Moser c o u l d n o t f i n d agreement w i t h S e e g e r ' s p r e d i c t i o n s . I t s h o u l d b e n o t i c e d t h a t R o d r i a n f o r Ta-0 used s m a l l i m p u r i t y c o n c e n t r a t i o n s (25 atppm 0 ) , whereas Magalas e t a l . worked i n range o f high concen- t r a t i o n s (1000 atppm C). I t i s i n t e r e s t i n q t o n o t e t h a t Magalas e t a l . c o n f i r m t h a t t h e SK peak develops a f t e r h e a t i n g t o 6 0 0 K
,
s u p p o r t i n n t h e s u g g e s t i o n o f Mondino, Seeger [13] on carbon-vacancy p a i r d i s s o c i a t i o n .2.4 Conclusions f o r b . c . c . m e t a l s . - A t t h i s c o n f e r e n c e i t appears c l e a r l y t h a t a c h a r a c t e r i s t i c r e l a x a t i o n spectrum can be proposed f o r d i s l o c a t i o n s i n b.c.c. m e t a l s :
-
KPF on non-screw d i s l o c a t i o n s i s l o c a t e d a t l o w temperatures w i t h ~ = 1 0 - ' p b 3 ( H a c t i v a t i o n e n t h a l p y , p shear modulus, b Burgers v e c t o r )-
KPF on screw d i s l o c a t i o n s appears n e a r t h e knee t e m p e r a t u r e o f t h e f l o w s t r e s s - t e m p e r a t u r e c u r v e w i t h ~ ~ 1 0 - ' p b3-
GKM peaks a r e l o c a t e d a t l o w temperatures a t t h e l o w t e m p e r a t u r e s i d e o f t h e KPF peak on non-screws. Here f u r t h e r i n v e s t i g a t i o n s w i l l be a p p r e c i a t e d- i n t e r a c t i o n peaks between H and d i s l o c a t i o n segments, (H-Snoek-Koester peaks), appear a t i n t e r m e d i a t e temperatures. I n V, Nb, Ta t h e s e peaks v e r y o f t e n dominate t h e l o w temperature spectrum. The Snoek-Koester peaks due t o 0, N, C i n t e r s t i t i a l s o l u t e atoms r e q u i r e f u r t h e r s y s t e m a t i c o b s e r v a t i o n s .
-
a t l o w e s t temperatures, below 10 K, s t i l l m o b i l e d i s l o c a t i o n segments a r e present, p r o b a b l y g e o m e t r i c a l k i n k s i n non-screw d i s l o c a t i o n s .3. D i s l o c a t i o n r e l a x a t i o n peaks i n f . c . c . m e t a l s . - I n Cu and d i l u t e Cu-Au a l l o y s , Schulz and Lenz s e p a r a t e an u l t r a s o n i c a t t e n u a t i o n (U.S.A.) spectrum w i t h d i f f e r e n t components due t o d i s l o c a t i o n resonance, KPF and phonon e l e c t r o n i n t e r a c t i o n . They f i n d t h e 2 Bordoni peaks i n t h e 10-50 YHz range and c o n f i r m i n t h i s range t h e w e l l - known v a l u e s H ~ 0 . 1 1 eV and s f o r t h e main peak. L a u z i e r and M i n i e r i n v e s - t i g a t e t h e s u b s t r u c t u r e o f t h e Bordoni peak i n Cu, w i t h t h e h e l p o f e l e c t r o n i r r a - d i a t i o n s and e l e c t r o n m i c r o s c o p i c o b s e r v a t i o n s and propose t h a t t h e w i d t h o f t h e Bordoni peaks cannot be e x p l a i n e d o n l y b y a H o r r o d i s t r i b u t i o n b u t must i n c l u d e r e - l a x a t i o n o f d i f f e r e n t t y p e s o f d i s l o c a t i o n s as suggested by Thompson and Holmes [14l.
These r e s u l t s a r e i m p o r t a n t a l s o f o r p o i n t d e f e c t s t u d i e s i n i r r a d i a t e d m e t a l s , where d i s l o c a t i o n s a r e used as a probe f o r m i g r a t i n g d e f e c t s .
A new e x p e r i m e n t a l t e c h n i q u e u s i n g U.S.A. measurements d u r i n g l o w f r e q u e n c y s t r a i n i n g o f t h e specimen i s p r e s e n t e d by Gremaud and B e n o i t : t h e y c o n f i r m t h a t t h e Bordoni r e 1 a x a t i o n i n A1 must be a s s o c i a t e d w i t h KPF on d i s l o c a t i o n s . D i r e c t measure- ments o f t h e i n t e r n a l s t r e s s i n s t r a i n e d A1 specimens, by d i p t e s t method, a r e p e r - formed by C h i c o i s , Hamel, Fougcres, Esnouf, F a n t o z z i , Perez; t h e y c o n f i r m t h e d i r e c t amp1 i t u d e c o r r e l a t i o n between t h e i n t e r n a l s t r e s s and t h e Bordoni r e 1 a x a t i o n i .e. t h e Park c o n d i t i o n .
By a s t u d y on deformed and H charged N i , Tanaka, Atsumi, Yamada, show t h a t H developpes a H - d i s l o c a t i o n i n t e r a c t i o n peak a t t h e expense o f t h e Bordoni peak. These two peaks seem t o be s i m i l a r t o t h e X and Y peaks shownby t h e e x p e r i m e n t s o f Besson and Boch [15], c o n f i r m i n g t h a t t h e l o w e r t e m p e r a t u r e peak i s t h e composed Bordoni peak ( Y ) and t h e o t h e r ( X ) an e x t r i n s i c peak. The work o f Seyed Reihani, Esnouf, F a n t o z z i
,
Revel, on Mg w i t h d i f f e r e n t p u r i t i e s , show c l e a r l y t h a t t h e p u r e Mg spectrum i s v e r y s i m i l a r as t h e A1 spectrum a f t e r d e f o r m a t i o n , o n t h e c o n t r a r y w i t h t h e l a r g e peak observed i n l e s s p u r e Mg; t h i s l a r g e peak i s caused b y d i s l o c a t i o n d e p i n n i n g .As a c o n c l u s i o n t h e p r e s e n t s t u d i e s on f . c . c . m e t a l s c o n f i r m t h e main c h a r a c t e r - i s t i c s o f t h e Bordoni r e l a x a t i o n peaks. F.c.c. m e t a l s ( i n c l u d i n g N i ) and h.c.p.
m e t a l s seem t o show an u n i f o r m spectrum w i t h 2 Bordoni r e l a x a t i o n peaks l o c a t e d a t low temperature, b u t experiments on o t h e r ( t h a n Mg) h.c.p. m e t a l s o f h i g h p u r i t y a r e needed t o c o n f i r m t h i s p o i n t o f view. The i n t e r p r e t a t i o n o f Bordoni r e l a x a t i o n as KPF on d i s l o c a t i o n s i s w e l l confirmed, b u t perhaps a t t e n t i o n must be focussed on t h e d i f f e r e n t t y p e s o f d i s l o c a t i o n s concerned w i t h Bordoni r e l a x a t i o n peaks.
C5-30 JOURNAL DE PHYSIQUE
References.-
1. G. Fantozzi, W. Benoit, C. Esnouf, and J. Perez, Annales de Physique - 4, 7 (1979) 2. R. H. Chambers, Physical Acoustics, v o l . 111 A, p. 123 (Ed. W. P. Mason)
Academic Press, New York, London (1966)
3. M. Maul and H. Schultz, t o be p u b l . S c r i p t a Met.
see a l s o : M. Maul, D i s s e r t a t i o n U n i v e r s i t P t S t u t t g a r t (1981) 4. R. Grau, D i s s e r t a t i o n U n i v e r s i t a t S t u t t g a r t (1981)
5. I . G. R i t c h i e , J. F. Dufresne, and P. Moser, phys. s t a t . s o l . ( a )
61,
591 (1980) 6. H. S c h u l t z and coworker, unpublished7. H. Schultz, t o be presented a t t h e I n t e r n . Conf. on p o i n t defects and d e f e c t i n t e r a c t i o n s i n Metals, Kyoto, Japan (1981)
8. A. Seeger and C. Wuthrich, I 1 Nuovo Cimento - 33 B, 38 (1976) 9. L. F. P. De Lima, These, EPFL, Lausanne (1981)
10. P. A s t i 6 , J. P. Peyrade e t P. Groh, S c r i p t a Met.
15,
477 (1981) see a l s o : P. A s t i 6 , These, U n i v e r s i t k de Toulouse (1981) 11. U. Rodrian, D i s s e r t a t i o n U n i v e r s i t a t S t u t t g a r t (1980) 12. A. Seeger, phys. s t a t . s o l . ( a ) - 55, 457 (1979) 13. M. Mondino and A. Seeger, S c r i p t a Met.-
11, 817 (1977)14. D. 0. Thompson and D. K. Holmes, J. Appl. Phys. - 30, 525 (1959) 15. J. L. Besson and P. Boch, I1 Nuovo Cimento
