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INTERNAL FRICTION STUDIES OF HEAVY
INTERSTITIAL IMPURITY ATOMS
C. Börner, K.-H. Robrock
To cite this version:
JOURNAL DE PHYSIQUE
Colloque C10, suppl6ment au 11'12, Tome 46, dgcembre 1985 page C10-55
INTERNAL FRICTION STUDIES OF HEAVY INTERSTITIAL IMPURITY ATOMS
lnstitut fur ~estkorperforschung, Kernforschungsanlage Julich, Postfach 1913, 0-5170 Julich, F.R.G.
A b s t r a c t . A s y s t e m a t i c i n t e r n a l f r i c t i o n s t u d y o f i r r a d i a t i o n - i n d u c e d i n t e r - s t i t i a l d e f e c t s i n d i l u t e Ag a l l o y s was c a r r i e d o u t by employing a newly de- veloped mu1 t i p l e sample h o l d e r . I n t e r n a l f r i c t i o n s p e c t r a were o b t a i n e d a f t e r i r r a d i a t i o n by 3 MeV e l e c t r o n s a t 5 K and a f t e r s e v e r a l subsequent a n n e a l i n g t r e a t m e n t s . The mu1 t i p 1 e sample h o l d e r p r o v i d e s a u n i f o r m t r e a t m e n t o f s i x samples i n b o t h i r r a d i a t i o n and mechanical t e s t c o n d i t i o n s .
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INTRODUCTIONF o r e i g n atoms i n m e t a l l i c a l l o y s which occupy s u b s t i t u t i o n a l s i t e s under thermal e q u i l i b r i u m c o n d i t i o n s may b e t r a n s f e r r e d i n t o i n t e r s t i t i a l s i t e s by t h e i r i n t e r a c - t i o n w i t h r a d i a t i o n induced s e l f - i n t e r s t i t i a l atoms. I n analogy t o t h e w e l l known Snoek e f f e c t , t h e l o c a l i z e d and/or l o n g range d i f f u s i o n o f t h e s e i n t e r s t i t i a l s o l u t e atoms may be i n v e s t i g a t e d by a n e l a s t i c r e l a x a t i o n methods p r o v i d e d t h a t t h e symmetry o f t h e e l a s t i c d i p o l e t e n s o r a s s o c i a t e d w i t h t h e i n t e r s t i t i a l atom i s l o w e r t h a n t h a t o f t h e c r y s t a l i n which i t i s embedded. I n t e r s t i t i a l s t r u c t u r e s as t h e y r e s u l t from model c a l c u l a t i o n s and from experimental o b s e r v a t i o n s have been discussed i n d e t a i l i n t h e preceeding ICIFUAS 7 /I/. From t h i s work f i g . 1 has been t a k e n i n o r d e r t o de- m o n s t r a t e t h e e f f e c t s t o be expected. The f i g u r e shows d i f f e r e n t c o n f i g u r a t i o n s o f p o s s i b l e s i t e s which u n d e r s i z e d f o r e i g n atoms may occupy upon t r a p p i n g and subsequent-
F i g . 1
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D i f f e r e n t arrangements o f i n t e r s t i t i a l s i t e s f o r u n d e r s i z e d s o l u t e atoms ( r e f . / I / ) . Jumps o f t h e s o l u t e atoms among t h e e q u i v a l e n t s i t e s o f each arrange- ment may g i v e r i s e t o a c h a r a c t e r i s t i c a n e l a s t i c r e l a x a t i o n e f f e c t .*permanent address : Institute for Fundamental Technological Research, Polish Academy of Sciences, Warsaw, Poland
C10-56 JOURNAL
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PHYSIQUEl y r e a c t i n g w i t h s e l f i n t e r s t i t i a l atoms. Jumps among t h e e q u i v a l e n t s i t e s o f t h e d i f f e r e n t c o n f i g u r a t i o n s g i v e r i s e t o a r e o r i e n t a t i o n o f t h e a s s o c i a t e d e l a s t i c d i - p o l e s and t h u s t o an a n e l a s t i c r e l a x a t i o n e f f e c t , e.g., an i n t e r n a l f r i c t i o n peak. T h i s r e l a x a t i o n l i n e may be used as a t a g t o i d e n t i f y p a r t i c u l a r i n t e r s t i t i a l c o n f i - g u r a t i o n s and
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s i n c e t h e r e l a x a t i o n s t r e n g t h i s p r o p o r t i o n a l t o t h e c o n c e n t r a t i o n-
t o f o l l o w t h e i r f a t e d u r i n g t h e p r o c e s s i n g procedures t o be s t u d i e d . I n t h i s manner one can study, f o r i n s t a n c e , t h e c o n t r i b u t i o n o f r a d i a t i o n - i n d u c e d i n t e r s t i t i a l so- l u t e atoms t o r a d i a t i o n - e n h a n c e d d i f f u s i o n and r a d i a t i o n - i n d u c e d s e g r e g a t i o n . T h i s i s t h e t o p i c o f t h e p r e s e n t paper.I 1
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EXPERIMENTALTowards t h i s aim, a new e x p e r i m e n t a l d e v i c e has been developed designed w i t h p a r t i - c u l a r a t t e n t i o n t o t h e needs f o r a s y s t e m a t i c i n t e r n a l f r i c t i o n study o f i n t e r s t i - t i a l s o l u t e atoms c r e a t e d by i r r a d i a t i o n i n a l l o y systems. Since i r r a d i a t i o n s , as i n t h e case o f 3 MeV e l e c t r o n i r r a d i a t i o n s employed i n t h e p r e s e n t work, a r e q u i t e t i m e consuming and s i n c e a comparative s t u d y r e q u i r e s i d e n t i c a l t r e a t m e n t o f t h e d i f - f e r e n t specimens, i t i s advantageous t o use a m u l t i p l e sample h o l d e r . As shown i n f i g . 2, t h e p r e s e n t l y used sample h o l d e r can t a k e up t o s i x i n t e r n a l f r i c t i o n sam- p l e s and a seventh sample o u t s i d e t h e i r r a d i a t i o n area s u p p o r t i n g t h e thermocouple f o r t e m p e r a t u r e measurements. The assembly can b e i n s e r t e d i n t o a H e - c r y o s t a t , i n which t h e i r r a d i a t i o n and t h e measurements a r e performed.
F i g . 2
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M u l t i p l e sample h o l d e r w i t h f i v e o f s i x i n t e r n a l f r i c t i o n samples mounted. A seventh sample on t h e l e f t serves t o s u p p o r t a thermocouple. The samples a r e clam- ped a t t h e top, t h e l o w e r ends a r e f r e e t o v i b r a t e . A sample f o r e l e c t r i c a l r e s i s t i - v i t y measurements i s mounted on t h e back b e h i n d t h e t r a p e z o i d a l g a u g e - s e c t i o n s o f t h e i n t e r n a l f r i c t i o n samples.I n f i g . 2 t h e i r r a d i a t i o n area covers a p p r o x i m a t e l y t h e r e c t a n g l e c o n t a i n i n g t h e narrow, t r a p e z o i d a l gauge s e c t i o n s o f t h e f i v e samples mounted on t h e r i g h t hand s i t e . The samples a r e clamped a t t h e t o p , t h e w i d e r r e c t a n g u l a r sample ends a t t h e b o t t o m s e r v e as e l e c t r o d e s f o r t h e c a p a c i t i v e p i c k - u p o f t h e sample v i b r a t i o n s . One o f t h e sample p o s i t i o n s i s l e f t unoccupied i n o r d e r t o show one o f t h e pick-up e l e c - t r o d e s mounted behind each o f t h e samples.
F i g . 3
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Sample shape ( t o p ) and s t r a i n d i s t r i b u t i o n (bottom) d u r i n g f l e x u r a l v i b r a t i o n s as o b t a i n e d by numerical i n t e g r a t i o n o f a d i f f e r e n t i a l equa- t i o n a p p r o p r i a t e f o r v i b r a t i o n s o f beams w i t h nonuniform cross s e c t i o n ( r e f . / 2 / ) .111
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RESULTSI n f i g . 4 i n t e r n a l f r i c t i o n spectra a r e shown as t h e y were o b t a i n e d f o r a pure Ag- sample and f i v e d i f f e r e n t Ag-alloys: &Cu, &Au, &Zn, &Pt, &A1 w i t h s o l u t e atom c o n c e n t r a t i o n s o f about 1000 atppm. A l l samples r e c e i v e d i r r a d i a t i o n w i t h e l e c t r o n s o f 3 MeV energy a t 5 K. The Frenkel d e f e c t c o n c e n t r a t i o n o f 300 atppm was o b t a i n e d by r e s i s t i v i t y measurements. A f t e r i r r a d i a t i o n t h e samples were annealed a t subse- q u e n t l y h i g h e r temperature. The s p e c t r a o f f i g . 4 were o b t a i n e d a f t e r annealing a t 45 K. Since m i g r a t i o n o f t h e s e l f i n t e r s t i t i a l atoms i n Ag occurs a t around 25 K
JOURNAL DE PHYSIQUE
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SUMMARYA newly developed m u l t i p l e sample h o l d e r f o r i n t e r n a l f r i c t i o n s t u d i e s o f f e r s ad- vantages o v e r c o n v e n t i o n a l s i n g l e sample heads w i t h r e s p e c t t o s a v i n g o f t i m e , i d e n - t i c a l sample t r e a t m e n t and i n s e n s i t i v i t y t o c l a m p i n g e f f e c t s and beam a p e r t u r e po- s i t i o n i n g i n t h e case o f i r r a d i a t i o n . Measurements on v a r i o u s s i l v e r a l l o y s a f t e r e l e c t r o n i r r a d i a t i o n show t h a t a p a i r o f peaks o c c u r s i n &-Cu w h i c h i s p o s s i b l y a s u i t a b l e c a n d i d a t e f o r s t u d y i n g t h e i n t e r s t i t i a l mechanism o f p r e f e r e n t i a l mass t r a n s p o r t d u r i n g i r r a d i a t i o n .
REFERENCES
/1/ K.-H. Robrock, J o u r n a l de physique C5-709 (1981), see a l s o : C5-729 and C5-735. - - . . . -
/2/ S. Timoshenko, Schwingungsprobleme d e r Technik, S p r i n g e r Verlag, B e r l i n 1932, p. 246.
