X-ray diffraction investigation of bimetallic diffusion zones in the Cu-Pd system
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should p r o v i d e k e y i n f o r m a t i o n in an a t t e m p t to r e l a t e the d e g r e e of d i f f u s i o n - g e n e r a t e d s u b g r a i n m i s o r i e n t a tion i n c r e a s e to the l a t t i c e p a r a m e t e r g r a d i e n t e x i s t i n g in the diffusion zone. To f a c i l i t a t e a c o m p a r i s o n of the r e s u l t s of t h i s i n v e s t i g a t i o n with t h o s e p r e v i o u s l y r e p o r t e d f o r the Cu-Nt and Cu-Au s y s t e m s , the s a m e e x p e r i m e n t a l t e c h n i q u e s w e r e u s e d to p r e p a r e the Cu s i n g l e c r y s t a l s and to c o l l e c t the X - r a y data. The c o n c e n t r a t i o n p r o f i l e s p r o d u c e d b y i s o t h e r m a l diffusion at 900~ w e r e d e t e r m i n e d b y m a t h e m a t i c a l a n a l y s e s of two d i f f r a c t e d i n t e n s i t y b a n d s . The B o l t z m a n n - M a t a n o a n a l y s i s was u s e d to e x t r a c t c o n c e n t r a t i o n - d e p e n d e n t diffusion c o e f f i c i e n t s which c o m p a r e d f a v o r a b l y with p r e v i o u s l y r e p o r t e d v a l u e s . Also, X - r a y r o c k i n g c u r v e s w e r e m a d e on s e l e c t e d c o m p o s i t i o n s to d e t e r m i n e the d e g r e e of d i f f u s i o n - g e n e r a t e d s u b g r a i n m i s o r t e n t a t i o n i n c r e a s e in the diffusion z o n e s . T H E O R E T I C A L CONSIDERATIONS The s p e c i m e n s u s e d in this i n v e s t i g a t i o n w e r e p r e p a r e d b y e l e c t r o p l a t t n g a thin l a y e r of Pd (8 ~tm) on one f a c e of a Cu s i n g l e c r y s t a l , cut and p o l i s h e d so that a [100] d i r e c t i o n was p e r p e n d i c u l a r to the s u r f a c e . When such a c o m p o s i t e s p e c i m e n is a n n e a l e d at a high t e m p e r a t u r e a c o m p l e t e s e r i e s of s o l i d s o l u t i o n s will be f o r m e d . The only c o m p o s i t i o n v a r i a t i o n s and, t h e r e f o r e , l a t t i c e p a r a m e t e r c h a n g e s will be p e r p e n d i c u l a r to the s u r f a c e of the s p e c i m e n . Equations for the d i f f r a c t e d i n t e n s i t y f r o m such a diffusion zone have b e e n r e p o r t e d tn p r e v i o u s p a p e r s . 1-~ If the diffusion zone i s s e c t i o n e d into thin s l a b s which span a s m a l l l a t t i c e p a r a m e t e r r a n g e f r o m a m - 89a a to a m + 89Aa, tt can be r e a d i l y shown that the s a m p l e d v o l u m e of m a t e r i a l a s s o c i a t e d with c o m p o s i t i o n C m is given by AVg-
DARREL R. TENNEY is Assistant Professor, Metallurgical Engineering, Division of Minerals Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Va. 24061. PATRICK K. TALTY is Research Metallurgist, Aerospace Research Laboratory (ARL-LL), Metallurgy and Ceramics Research Laboratory, WrightPatterson AFB, Ohio 45433. Manuscript submitted October 24, 1972. METALLURGICAL TRANSACTIONS
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