Interdiffusion in copper-base Cu-AI solid solutions
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interdiffusion in solid solutions of aluminum in copper has been studied by several investigatorsX-S to a limited extent. An extensive investigation has been done recently in the present authors' laboratory (Refs. 4 and 5), but it has become apparent that the alloy used in the investigation was not a suitable one: segregation of aluminum was found in some specimens. In this investigation interdiffusion coefficients and the Kirkendall effect are studied using a sound alloy. EXPERIMENTAL PROCEDURE The diffusion c o u p l e s w e r e p r e p a r e d f r o m v a c u u m m e l t e d h i g h - p u r i t y c o p p e r (99.99+ pet) and a Cu-12.2 at. pct Al alloy. The a l lo y d i s c s , 10 m m long and 12 m m in d i a m , w e r e m a c h i n e d f r o m an ingot which had b e e n h o m o g e n i z e d at 1274 K for about 0.35 Ms. The c o p p e r d i s c s of s i m i l a r d i m e n s i o n s w e r e m a c h i n e d f r o m a f o r g e d ingot. S a n d w i c h - t y p e diffusion c o u p l e s w e r e m a d e by p r e s s u r e - w e l d i n g of an a l l o y d i s c s b e tw e en two c o p p e r d i s c s or v i c e v e r s a at 923 K in a v a c uum of about 0.1 m P a . The t i m e n e c e s s a r y to obtain a sound weld was about 5.4 ks. The depth of d if f u si o n d u r i n g this wel d i n g was l e s s than 0.5 pet of the final diffusion depth. Couples w e r e e x a m i n e d m e t a l l o g r a p h i c a l l y f o r weld d e f e c t s b e f o r e d i f f u s i o n annealing. Diffusion a n n e a l i n g was p e r f o r m e d in e v a c u a t e d q u a r t z c a p s u l e s in the t e m p e r a t u r e r a n g e b e t w e e n 977 and 1277 K. C o n c e n t r a t i o n - p e n e t r a t i o n c u r v e s of d i f f u s i o n - t r e a t e d s a m p l e s were established using a m i c r o p r o b e analyzer. The i n t e n s i t y of AlKcr r a d i a t i o n w a s m e a s u r e d in 5 ~tmto 50 ~ t m - s t e p s f o r t h r e e d i f f e r e n t t r a v e r s e s of about 1 m m long a c r o s s the i n t e r f a c e , and then a v e r a g e d to obtain the final p r o f i l e . A l i n e a r r e l a t i o n b e t w e e n the r a d i a t i o n i n t e n s i t y and the c o n c e n t r a t i o n of a l u m i n u m was a s s u m e d u s i n g nondiffused p a r t s of the couple as the s t a n d a r d s . I n t e r d i f f u s i o n c o e f f i c i e n t s , D, w e r e c a l c u l a t e d by the M a t a n o - B o l t z m a n method, e V a l u e s at the i n f i n i t e s i m a l NOBUO MATSUNO, formerly a Graduate Student, Department o f Materials Science, Tohoku University, is now with Chiba Works, Kawasaki Steel Corp., Chiba, Japan. HIROSHI OIKAWA is Associate Professor, Department of Materials Science, Faculty of Engineering, Tohoku University, Sendal 980, Japan. Manuscript submitted April 1, 1975. METALLURGICAL TRANSACTIONSA
c o n c e n t r a t i o n of a l u m i n u m , /~ (NA1 ~ 0), w e r e d e t e r m i n e d by the Hall m et h o d . 6 The e s t i m a t e d e r r o r i n / ~ is about +10 pet. Although no m a r k
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