TRAPPING OF SELF-INTERSTITIALS AT OVERSIZED IMPURITIES IN Al-Mg AND Cu-In AND UNDERSIZED IMPURITIES IN Al-Fe

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TRAPPING OF SELF-INTERSTITIALS AT OVERSIZED IMPURITIES IN Al-Mg AND Cu-In

AND UNDERSIZED IMPURITIES IN Al-Fe

G. Kollers, H. Jacques, L. Rehn, K.-H. Robrock

To cite this version:

G. Kollers, H. Jacques, L. Rehn, K.-H. Robrock. TRAPPING OF SELF-INTERSTITIALS AT OVER-

SIZED IMPURITIES IN Al-Mg AND Cu-In AND UNDERSIZED IMPURITIES IN Al-Fe. Journal de

Physique Colloques, 1981, 42 (C5), pp.C5-729-C5-733. �10.1051/jphyscol:19815112�. �jpa-00220981�

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JOURNAL DE PPHSIQUE

CoZZoque C 5 , suppldmt?nt a u nO1O, Tome 42, o c t o b r e 1981 _{p a g e}c5-729

TRAPPING OF SELF-INTERSTITIALS AT OVERSIZED IMPURITIES IN

&-Mg

AND

Cu-In

AND UNDERSIZED IMPURITIES IN

&-Fe

-

G. K o l l e r s , H . J a c q u e s , L.E. ~ e h n * and K.-H. Robrock

I n s t i t u t fEi* Festkiirperforschttng, KemforschungsanZage Jiilich, 0-5170 JiiZ<ch, F.

H.

G.

" ~ r ~ o n i z e NationuZ L a b o r a t o r y , M a t e r i a l s S c i e n c e D i v i s i o n , Argonne, I Z Z i n o i s 60439, U.S.A.

A b s t r a c t . - S e v e r a l IF-peaks have been o b s e r v e d i n Al-0.04at% F e , Al-O.Olat%

Mg and Cu-0.025at% I n a f t e r e l e c t r o n i r r a d i a t i o n s . These peaks c a n a l l b e r e l a t e d t o r e o r i e n t a t i o n p r o c e s s e s o f p o i n t - d e f e c t complexes c o n s i s t i n g o f s e l f - i n t e r s t i t i a l and i m p x i t y a t o m s . The a c t i v a t i o n e n e r g i e s and preexpo- n e n t i a l f a c t o r s a r c f o u n d i n a r a n g e which i s c h a r a c t e r i s t i c f o r i n t e r s t i - t i a l - a t o m jwnps. The p e a k b e h a v i o u r d u r i n g t h e r m a l a n n e a l i n g t r e a t m e n t s r e - v e a l tine t r a p p i n g - s t r e n g t h o f i m p u r i t y atoms f o r m i g r a t i n g s e l f - i n t e r s t i - t i a l - a t o m s .

I n t r o d u c t i o n . - T r a p p i n g of' m i g r a t i n g s e l f - i n t e r s t i t i a l s ( S ) a t i m p u r i t y atoms ( I ) i s f r e q u e n t l y o b s e r v e d i n a l l o y s u n d e r i r r a d i a t i o n / I / . It r e s u l t s i n t h e f o r m a t i o n o f s o - c a l l e d S1-complexes which a r e a g g l o m e r a t e s o f one o r more S and one o r more I .

The f o r m a t i o n and p r o p e r t i e s of SI-complexes have a t t r a c t e d c o n s i d e r a b l e a t t e n - t i o n i n t h e p a s t and many a l l o y s have b e e n s t u d i e d .

The p r e s e n t I F - s t u d i e s on &-In have beer. i n i t i a t e d b e c a u s e o f a c o n t r o v e r s y which a r o s e i n t h e i n t e r p r e t a t i o n of damage r a t e s t u d i e s / 2 / and P e r t u r b e d Angular

C o r r e l a t i o n - s t u d i e s /3/ on t h e same a l l o y namely a b o u t t h e q u e s t i o n a f t e r t h e t h e r - mal s t a b i l i t y o f t h e SI-complexes i n &-In.

A f u r t h e r aim o f t h e p r e s e n t work was t o compare t h e r e s u l t s on =-In w i t h ana- l o g o u s I F - r e s u l t s on g - M g and 4 - E ' e . I t was t h o u g h t t h e t t h i s might g i v e i n s i g h t i n t o t h e r a n g e o f v a l i d i t y o f t h e o r e t i c a l models d e v e l o p e d r e c e n t l y / 4 , 5 / .

E x p e r i m e n t a l . - Cu samples c o n t a i n i n g 250 atppm I n and A 1 s a m p l e s c o n t a i n i n g 125 atppm Mg a n d 400 atppm F e , r e s p e c t i v e l y , have b e e n i r r a d i a t e d a t 4.5K w i t h 3 MeV e l e c t r o n s a t t h e low t e m 7 e r a t u r e i r r a d i a t i o n f a c i l i t y o f lCFA J u l i c h . The s u b s e q u e n t i n t e r n ~ l f r i c t i o n measurements of 4 - F e and &-Mg were c a r r i e d o u t i n a low f r e q u e n c y t o r s i o n pendulum, t h e measurements on &-In i n a v i b r a t i n g r e e d a p p a r a t u s . The d e f e c t c o n c e n t r a t i o n s i n t r o d u c e d by t h e i r r a d i a t i o n were m o n i t o r e d by s i m u l t a n e o u s l y i r r a d i a t e d r e s i s t i v i t y s a m p l e s .

R e s u l t s . - S i x IF-peaks were o b s e r v e d i n %-In, f i v e i n &-Mg and s i x p e a k s i n E - F e . The c h a r a c t e r i s t i c s o f t h e s e peaks a r e summarized i n t a b l e 1 , e x c e p t f o r two o f them i n &-Fe, which were t o o s m a l l i n o r d e r t o b e a n a l y z e d i n g r e a t e r d e t a i l .

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19815112

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JOLTRNAL DE PHYSIQUE

t a b l e 1

Peak Tp/K HR/eV r 0 / s

mat. n o .

Peak c h a r a c t e r i s t i c s o f IF-peaks o b s e r v e d i n Al-0 .OL%Fe, A1-0 .O1%Mg and Cu-0.025%In af'er e l e c t r o n i r r a d i a t i o n : T p = p e F t e m p e r a t u r e ; H R = a c t l v a t i o n e n e r e y o f

d e f e c t r e o r i e n t a t i o n ; r , = p r e e x p o n e n t i a l o f r e -

l a x a t i o n t i m e

CuIn I 54.5 < 1 0 -

11 11 ¹

7+2

3. ,(,-I '+I

111 4 8 Y0+_10 1. 10-12z1

I V 57.5 110+_10 3. 10-12+'

V 85 15351 5 2. lo-12?1

V I 110 20922 I

6.

0-l

321

T a b l e 1 shows t h e peak t e m p e r a t u r e , T a t a b o u t 80 Hz, t h e a c t i v a t i o n e n e r g y , P '

H R , f o r t h e r e o r i e n t a t i o n and t h e p r e e x p o n e n t i a l o f t h e r e l a x a t i o n t i m e , T ~ . P r a c - t i c a l l y a l l of t h e v a l u e s l i s t e d i n t a b l e 1 f a l l i n a r a n g e which i s t y p i c a l f o r r e o r i e n t a t i o n jumps of s i n g l e o r m u l t i p l e s e l f - i n t e r s t i t i u l s / 6 , 7 , 8 / .

Of p a r t i c u l a r i n t e r e s t i s t h e a n n e a l i : l g b e h a v i o u r o f t h e IF-peaks, b e c a u s e t h e y d i r e c t l y r e f l e c t t h e f o r m a t i o n - and a n n i h i l a t i o n p r o c e s s e s o f t h e v a r i o u s i n d i v i - d u a l SI-complexes p r e s e n t i n t h e s a m p l e s . The r e s u l t s a r e shown i n f i g , 1 , where t h e peak h e i g h t s n o r m a l i z e d t o t h e i r maximum h e i g h t , Q - l , o b t a i n e d d u r i n g t h e t e m p e r i n g t r e a t n e n t a r e p l o t t e d a s a f u n c t i o n of' t h e t e m p e r i n g t e m p e r a t u r e s . D i s c u s s i o n . - 1 . ) Peak c h a r a c t e r i s t i c s : The p e a k s c h a r a c t e r i z e d i n t a b l e 1 a r e o n l y o b s e r v e d i n t h e s p e c i f i e d a l l o y s and n o t i n p u r e Al o r p u r e Cu. T h e r e f o r e t h e peaks have t o b e a t t r i b u t e d t o t h e s t r e s s i n d u c e d r e o r i e n t a t i o n o f SI-complexes. Of ? a r - t i c u l a r i n t e r e s t i n r e s p e c t Lo t h e peak c h a r a c t e r i s t i c s a r e t h e two p e a k s o c c u r i n g below 10K i n g - F e and &-In. The a t o m i c jump mechanism u n d e r l y i n g t h e 8K-peak i n A1-Pe i s d e s c r i b e d i n d e t a i l i n a n o t h e r c o n t r i b u t i o n t o t h i s c o n f e r e n c e / 8 / . There

-

it i s shown, t h a t t h e peak r e s u l t s from a motion o f an i n t e r s t i t i a l - F e - a t o m l i k e i n a cage i n s i d e a u n i t c e l l of t h e f c c l a t t i c e . A s p e c i f i c model f o r t h e low tem- p e r a t u r e peak o b s e r v e d i n &-In h a s n o t y e t b e e n d e v e l o p e d .

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I 1

2 . ) Number of IF-peak : The num- b e r o f IF-peaks o b s e r v e d i n e a c h of t h e t h r e e d i f f e r e n t samples i s a p p a r e n t l y l a r g e i n s p i t e of t h e s K a l l S- and I - c o n c e n t r a t i m i n t h e s a m p l e s . T h i s r u l t i p l i -

I c i t y may have two d i f f e r e n t o r i - g i n s : ( i ) One g i v e n d e f e c t t y p e

A I

may g i v e r i s e t o more t h a n one

1

c a s e s may b e d i s t i n g u i s h e d from

1 0,s

0 ,

1 e a c h o t h e r from t h e a n n e a l i n g

I

b e h a v i o u r o f t h e p e a k s : If p e a k s a r e b e i n g formed o r d i s a p p e a r a t

0.5

d i f f e r e n t a n n e a l i n g t e m p e r a t u r e s ,

t h e y must a s a n e c e s s i t y b e at- t r i b u t e d t o d i f f e r e n t t y p e s

0

o f S I - c o m ~ l e x e s . With t h i s c r i -

- A I - M g

- - I1 I

- -

m

- - - IV

-

^V

20 30

Lo

50 -- loo ^To 200 300 ^{[ K I}

t e r i o n , i n a - F e a t l e a s t t h r e e d i f f e r e n t SI-complexes have been o b s e r v e d , a t l e a s t two i n &-Mg IF-peaks v i a d i f f e r e n t r e l a x a - t i o n modes. An example o f t h i s i s t h e p a i r o f t h e 8K and 4 2 ~ peak i n a - F e / 8 / . ( i i ) S e v e r a l d i f f e r e n t SI-complexes may b e p r e s e n t i n t h e s a m p l e . These two

and a t l e a s t . f i v e i n &-In, a s P i g . 1 : Normalized peak h e i g h t s a s a f u n c t i o n o f

a n n e a l i n g t e m p e r a t u r e Ta. Q,' i s t h e max. c a n b e s e e n fron: f i g . 1

.

^{F o r}

p e a k h e i g h t o b t a i n e d d u r i n g t h e t e m p e r i n g Cu-In it h a s been shown t h a t t r e a t m e n t . The peak numbers c o r r e s p o n d t o

-

t h e peak numbers g i v e n i n t a b l e 1 . t h i s o b s e r v a t i o n c a n b e explained by a SI-complex e n s e n b l e , which c o n s i s t s o f d i f f e r e n t l y l a r g e SI-complexes, namelycomplexescontainingfrom one t o f i v e S bound a t one I-atom / 9 / . A s i m i l a r d e f e c t ensemble may a l s o a c c o u n t f o r t h e s e v e r a l p e a k s o b s e r v e d i n &-Fe and g - M g .

3 . ) B i n d i n g e n e r g i e s : The most s t a b l e SI-complexes d i s a p p e a r i n g-Mg and &-In a t a n n e a l i n g t e m p e r a t u r e s o f a b o u t 150K. I n a c c o r d a n c e w i t h t h e i n t e r p r e t a t i o n o f damage r a t e measurements on &-Mg / l o / a n 8 s - I n / 2 / t h i s r e c o v e r y i s a t k r i b u t e d t o d i s s o c i a t i o n p r o c e s s o f t h e most s t a b l e SI-complexes. I f t h i s a s s i g n m e n t i s c o r r e c t , b i n d i n g e n e r g i e s o f a b o u t 0.35 eV c a n b e deduced f o r t h e s e complexes / I / .

The SI-complexes i n &-Pe a r e much more s t a b l e . They remain i n t h e sample up t o a b o u t 2OOK, where t h e y are a c n i h i l a t e d by m i g r a t i n g v a c a n c i e s ( s t a g e 111). T h e r e f o r e

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C5-732 JOURNAL DE PHYSIQUE

only a lower l i m i t f o r t h e binding- o r f o r t h e m i g r a t i o n e n e r g i e s of t h e s e SI-com- p l r x e s can be g i v e n which i s 0.5 eV / I / .

4 . ) Comparison with theory : So f a r t h e r e i s only one model a v a i l a b l e which accounts f o r t h e d i f f e r e n c e s i n t r a p p i n g p r o p e r t i e s of d i f f e r e n t s o l u t e atoms i n terms of a simple p h y s i c a l parameter. T h i s parameter i s t h e s o - c a l l e d volume m i s f i t , 6 , which i s t h e r e l a t i v e r e l a x a t i o n volune of t h e I i n s o l u t i o n . I f 6 > 0 , s o l u t e s a r e c a l l e d o v e r s i z e d and i f 6 < 0 , undersized.

I n accordsnce with what i s expected from t h e model it h a s been found i n s e v e r a l c a s e s t h a t undersized I s e t t l e down i n t o i n t e r s t i t i a l s i t e s upon trapp'ing a S / I / .

I n f i g . 2a a c o n f i g u r a t i o n i s shown where t h e r e a r e 24 equi-

-

v a l e n t s i t e s f o r t h e i n t e r s t i - t i a l I e s t a b l i s h i n g a cage i n which t h e I-atom jumps around.

many /8/, which e x p l a i n s t h e

I - 7

u n d e r s i z e d s o l u t e atoms having

u

t r a p p e d a s e l f - i n t e r s t i t i a l atom.

I f o v e r s i z e d I encounter a F i g . 2 : ( a ) Cage model of a SI-complex c o n t a i n i n g

an undersized s o l u t e atom. ( b )

.im

model m i g r a t i n g S t h e S i s trapped - ^A

which e x p l a i n s j~unps of s e l f - i n t e r s t i t i a l a s a r e g u l a r dumbbell on a

dumbbells around a; o v e r s i z e d impurity -

atom. n e a r e s t neighbour s i t e of t h e

I which remains on t h e s u b s t i - t u t i o n a l s i t e , a s shown i n f i g . 2b. The dumbbell can jump around t h e I l i k e on a l e a s h . T h i s motion i s a t y p i c a l S-jump mode which i s expected t o g i v e r i s e t o an IF-peak. The abundance of peaks observed i n fi-Mg and %-In may b e e x p l a i n e d by t h e f a c t t h a t such dumbbell jumps l i k e on a l e a s h do n o t occur only f o r a s i n g l e S t r a p p e d a t a I , b u t a l s o i f more t h a n one S a r e t r a p p e d .

Conclusions.- In each of t h e t h r e e i r r a d i a t e d a l l o y s , &-Fe, &-Mg and &-In an ensemble of d i f f e r e n t l y s t r u c t u r e d self-interstitial-Lmpurity atom complexes e x i s t s . T h i s means t h a t even a t a low c o n c e n t r a t i o n r a t i o of cS/cI ^%% 0.1

...

0 . 2 not only one dominant de:'ect i s b e i n g formed b u t a d i s t r i b u t i o n of v a r i o u s SI-complexes.

The t r a p p i n g s t r e n g t h may be d i f f e r e n t f o r d i f f e r e n t I , i . e . f i n a l d e t r a p p i n g occurs i n &-In a t 140K, i n &-Mg a t 1 6 0 ~ and beyond 2OOK i n

4-Fe .

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. ,

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