THE BEHAVIOR OF TIN DURING AGING OF Al-Cu-Sn ALLOYS

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THE BEHAVIOR OF TIN DURING AGING OF Al-Cu-Sn ALLOYS

M. Taniwaki, S. Umeyama, Y. Ishida

To cite this version:

M. Taniwaki, S. Umeyama, Y. Ishida. THE BEHAVIOR OF TIN DURING AGING OF Al-Cu-Sn AL- LOYS. Journal de Physique Colloques, 1979, 40 (C2), pp.C2-549-C2-550. �10.1051/jphyscol:19792190�.

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JOURNAL DE PHYSIQUE

Colloque C2, suppl6ment au n o 3, Tome

mars 1979, page C2-549

THE BEHAVIOR OF TIN DURING AGING OF

M . Taniwaki, S. Umeyama and Y. I s h i d a

I n s t i t u t e of Industrial Science, University of Tokyo, 7 Roppongi, Minato, Tokyo, J a p m

RLsurn6.- Le s p e c t r e Mgssbauer d e '19Sn d a n s l ' a l l i a g e Al-Cu-Sn e s t e n r e g i s t r g p e n d a n t d e s r e c u i t s i s o t h e r m s 1 d i f f d r e n t e s t e m p g r a t u r e s . Les e f f e t s d e s atomes d e Sn s u r l e d u r c i s s e m e n t s t r u c t u r a l d e l ' a l l i a g e s o n t d i s c u t d s . I1 a p p a r a F t que 1 ' 6 t a i n i n t e r a g i t a v e c l e s atomes d e c u i v r e p e n d a n t l e v i e i l l i s s e m e n t 1 300 K. Au-dessus de 400 K , i l y a f o r m a t i o n d ' u n c l u s t e r a v e c d e s l a c u n e s e t ( o u ) d e s atomes d e c u i v r e .

A b s t r a c t . - The Mgssbauer s p e c t r u m of l19Sn i n t h e Al-Cu-Sn a l l o y i s measured d u r i n g i s o t h e r m a l annea- l i n g a t v a r i o u s t e m p e r a t u r e s and e f f e c t s of Sn atoms on t h e age h a r d e n i n g of t h e a l l o y a r e d i s c u s s e d . I t i s concluded t h a t t i n i n t e r a c t s w i t h Cu atoms d u r i n g a g i n g a t a b o u t 300 K. A t above 400 K. i t forms a c l u s t e r w i t h v a c a n c i e s a n d / o r Cu atoms.

1 . I n t r o d u c t i o n . - T r a c e e l e m e n t s s u c h a s Cd, I n and Sn i n f l u e n c e t h e a g i n g p r o c e s s of aluminium a l l o y s / l - 3 1 , b u t t h e mechanism h a s n o t b e e n c l a r i f i e d y e t . C o n v e n t i o n a l e x p e r i m e n t a l methods s u c h a s r e s i s t i v i - t y measurement a r e n o t d i r e c t enough t o t r a c e t h e b e h a v i o r s of t h e minor e l e m e n t s i n a l l o y s . Mzssbauer s p e c t r o s c o p y h a s an a d v a n t a g e f o r s u c h s t u d i e s . I n t h e p r e v i o u s r e p o r t t h e p r e s e n t a u t h o r s showed t h a t t h e change of s p e c t r u m of l 1 9 s n i n t h e Al-Cu-Sn a l - l o y d u r i n g i s o c h r o n a l a n n e a l i n g c o r r e s p o n d e d t o t h e change of t h e h a r d n e s s 141. I n t h i s r e p o r t , d e t a i l e d measurements of Massbauer s p e c t r a d u r i n g i s o t h e r m a l a g i n g a t v a r i o u s t e m p e r a t u r e a r e performed and t h e e f f e c t s o f Sn atoms on t h e a g i n g p r o c e s s a r e d i s c u s - s e d .

2. Experimenta1s.- A l l o y s were produced by m e l t i n g 99.999% A l , 99.998% Cu and 80% e n r i c h e d '19Sn i n t h e h i g h p u r i t y a l u m i n a c r u c i b l e . An A1-3.4ZCu-0.028ZSn a l l o y was u s e d f o r a g i n g e x p e r i m e n t s a t above 400 K and an AI-2.O%Cu-0.028XSn a l l o y was u s e d f o r a g i n g e x p e r i m e n t s below t h e t e m p e r a t u r e . Specimens were s o l u t i o n - t r e a t e d i n A r atmosphere a t 798 K f o r 3h.

I s o t h e r m a l a n n e a l i n g was performed a t 303, 333 K ( s o - c a l l e d low t e m p e r a t u r e a g i n g ) and 423, 453 K ( h i g h t e m p e r a t u r e a g i n g ) . A f t e r s u b s e q u e n t a n n e a l i n g . Massbauer s p e c t r u m was measured. F o r t h e h i g h tempe- r a t u r e a g i n g e x p e r i m e n t s , V i c k e r s h a r d n e s s was a l s o measured. F o r comparison, t h e Msssbauer s p e c t r u m o f l l 9 S n i n 0 p h a s e was a l s o measured. Obtained s p e c t r a were a n a l y z e d by s i n g l e L o r e n t z i a n l i n e u s i n g t h e

l e a s t - s q u a r e s method.

3. R e s u l t s . - F i g u r e I shows an example of s p e c t r a . Changes of Massbauer p a r a m e t e r s and V i c k e r s h a r d n e s s d u r i n g t h e i s o t h e r m a l a n n e a l i n g a r e shown i n f i g u r e

2 and f i g u r e 3.

( A I

F i g . I : Mzssbauer s p e c t r a of l 1 9 s n i n Al-Cu-Sn a l - l o y s . (A) quenched from 798 K; (B) a n n e a l e d a t 303 K f o r 720 m i n u t e s ; (C) a n n e a l e d a t 423 K f o r 6 0 m i n u t e s

L i n e a r e a s were n o r m a l i z e d by t h a t of t h e quenched s t a t e . L i n e p o s i t i o n were measured r e l a t i v e t o BaSnO, a t room t e m p e r a t u r e . The s p e c t r u m of t h e quenched s t a t e was almost t h e same a s t h a t of t h e quenched AI-Sn a l l o y . Sn atoms i n t h e quenched a l l o y d o e s n ' t seem t o b e a f f e c t e d by Cu atoms.

F i g u r e 2 shows t h e e f f e c t s of low tempera- t u r e a g i n g . During a n n e a l i n g a t 303 K , l i n e a r e a , p o s i t i o n and w i d t h i n c r e a s e d monotonously. During a n n e a l i n g a t 333 K , on t h e o t h e r hand, t h e y k e p t i n c r e a s i n g f o r 60 m i n u t e s and t h e n began t o d e c r e a s e .

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19792190

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F i g . 2 : Changes i n t h e MEssbauer s p e c t r u m parameters d u r i n g a g i n g a t 303 K

1 (-

The i n c r e a s e of l i n e p o s i t i o n was caused by t h e growth o f a new component a t t h e h i g h e r v e l o c i t y s i d e of t h e spectrum. The i n c r e a s e i n t h e l i n e a r e a s h o w e d t h a t t h e r e c o i l l e s s f r a c t i o n of t h e new component was l a r g e r t h a n t h a t o f a s quenched specimen. The d e c r e a s e i n t h e l i n e a r e a d u r i n g a n n e a l i n g a t 333 K a f t e r 90 m i n u t e s was caused by a n o t h e r component of t h e s p e c t r u m whose r e c o i l l e s s f r a c t i o n was low.

\*.*W/-.--- ___..----

A r e a

....

...

F i g . 3 : Changes i n t h e s p e c t r u m p a r a m e t e r s and V i c k e r s h a r d n e s s , d u r i n g a g i n g a t 4 2 3 K (-b---b-)

and 453 K (-M-)

F i g u r e 3 shows t h e e f f e c t s of t h e h i g h tempe- r a t u r e a g i n g . The l i n e a r e a showed deep minimum a f - t e r a g i n g f o r 5 m i n u t e s a t 4 5 3 K and f o r 60 m i n u t e s a t 4 2 3 K, j u s t b e f o r e t h e V i c k e r s h a r d n e s s began t o i n c r e a s e . The l i n e p o s i t i o n i n i t i a l l y i n c r e a s e d and t h e n d e c r e a s e d d u r i n g a g i n g p r o c e s s . The l a r g e i n -

c r e a s e of l i n e p o s i t i o n showed t h a t n e a r l y a l l o f s n atoms changed t h e i r s t a t e . The s e c o i l l e s s f r a c t i o n of Sn atoms i n t h i s new s t a t e were lower t h a n t h a t of quenched s t a t e . When t h e V i c k e r s h a r d n e s s r e a c h e d t h e maximum, t h e s p e c t r u m was a l m o s t t h e same a s t h a t of '19sn i n 8 phase. I t i s known t h a t t h e maxi- mum h a r d n e s s i s o b t a i n e d when t h e 8 ' p h a s e h a s p r e - c i p i t a t e d . Sn atoms seem t o b e a s s o c i a t e d w i t h 8' phase a t t h i s s t a g e .

4. D i s c u s s i o n . - During t h e a n n e a l i n g of quenched Al-Cu-Sn a l l o y s , two new s t a t e s o f Sn atoms were de-

t e c t e d . One of them was formed d u r i n g low temperature a g i n g ( c a l l e d Sn(A) h e r e a f t e r ) . The o t h e r was formed a t h i g h t e m p e r a t u r e a g i n g ( c a l l e d S n ( B ) ) . The s t a t e of Sn atoms formed a t t h e l a t e r s t a g e o f 333 K annea- l i n g seems t o be t h e i n i t i a l s t a g e of %(B). The l i n e p o s i t i o n o f b o t h s t a t e s was i n t h e h i g h e r v e l o c i t y s i d e . The r e c o i l l e s s f r a c t i o n o f Sn(A) was h i g h and t h a t of Sn(B) was e x t r e m e l y low. Sn(A) i s r e s p o n s i - b l e f o r t h e r e t a r d a t i o n of low t e m p e r a t u r e a g i n g and Sn(B) f o r t h e a c c e l e r a t i o n o f t h e h i g h t e m p e r a t u r e a g i n g .

I n t h e quenched A1-Sn a l l o y , a s t a t e of Sn atoms bound a s weak a s t h a t of Sn(B) was a l s o formed / S / , and t h e l i n e p o s i t i o n was i n h i g h v e l o c i t y side.

The s t a t e of Sn was a t t r i b u t e d t o t h e c l u s t e r of Sn atoms and v a c a n c i e s . I t i s supposed t h a t Sn(B) cor- r e s p o n d s t o t h e c l u s t e r of Sn atoms and v a c a n c i e s . However t h e l i n e p o s i t i o n of Sn(B) was somewhat d i f - f e r e n t from t h a t of Sn i n t h e Al-Sn a l l o y . It may mean c h a t t h e s t a t e o f Sn atoms formed p r i o r t o t h e h i g h t e m p e r a t u r e a g i n g is u n d e r t h e d i r e c t i n f l u e n c e of Cu atoms.

Sn(A), a b s e n t i n t h e AI-Sn a l l o y , seems t o b e i n f l u e n c e d by Cu atoms, s u g g e s t i n g t h e i n t e r a c t i o n between Sn and Cu atoms. During low t e m p e r a t u r e a g i n g , Cu atoms may b e a s s o c i a t e d w i t h quenched-in vacancies and m i g r a t e . Sn atoms seem t o t r a p t h e m i g r a t i n g Cu- vacancy a g g r e g a t e s and r e t a r d t h e age h a r d e n i n g .

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