Diffusion of the tracers Cu 67 , Ni 66 , and Zn 65 in copper-rich solid solutions in the system Cu-Ni-Zn
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ANUSAVICE AND R. T. D e H O F F
T r a c e r diffusion c o e f f i c i e n t s w e r e d e t e r m i n e d f o r the t h r e e i s o t o p e s , Zn 65, Cu 67, and Ni 66, in h o m o g e n e o u s C u - N i - Z n b i n a r y and t e r n a r y a l l o y s , to 30 pct Ni and Zn, and p u r e c o p p e r a s a function of c o m p o s i t i o n a n d a s a function of t e m p e r a t u r e , within about 250~ of the s o l i d u s s u r f a c e . A c t i v a t i o n e n e r g i e s and Do f a c t o r s w e r e d e t e r m i n e d a s functions of c o m p o s i t i o n f r o m t h e s e m e a s u r e m e n t s . It i s found that a s t h e c o m p o s i t i o n p l a n e i s t r a v e r s e d in the g e n e r a l d i r e c t i o n f r o m high n i c k e l c o m p o s i t i o n s on t h e c o p p e r - n i c k e l b i n a r y to high zinc c o n c e n t r a t i o n s on the c o p p e r - z i n c b i n a r y , i.e., a s n i c k e l i s r e p l a c e d by z i n c , the diffus i v i t y of a l l t h r e e t r a c e r s i n c r e a s e s , and the a c t i v a t i o n e n e r g y f o r diffusion d e c r e a s e s . The t o t a l change in d i f f u s i v i t y a c r o s s the c o m p o s i t i o n p l a n e i s about two o r d e r s of m a g n i tude. T h e t h r e e d i f f u s i v i t i e s a r e a l w a y s in the o r d e r : /~Zn > D~u > D~i, with the r a t i o b e i n g 9:3:1 at 900~ f o r a l l c o m p o s i t i o n s . The t h r e e a c t i v a t i o n e n e r g i e s a r e u s u a l l y in the o r d e r Q~i > Q~u > Q~n. T h e s e r e s u l t s a r e shown to be c o n s i s t e n t with a t o m s i z e and e l e c t r o n - t o a t o m c o n c e n t r a t i o n s of the t h r e e s p e c i e s in t h i s a l l o y s y s t e m .
A l o ne x p egr i m e n-t a l rp r o gar a m na t thegU n iev e r s i t y of F l o r i d a on the c o m p l e t e a n a l y s i s of diffusion b e h a v i o r in a s i n g l e t e r n a r y s y s t e m h a s c o n c e n t r a t e d upon the fcc s o l i d solution in the s y s t e m C u - N i - Z n . The o b j e c t i v e s of t h i s p r o g r a m a r e : 1) to p r o v i d e the e x p e r i m e n t a l i n f o r m a t i o n which i s n e c e s s a r y f o r a s s e s s i n g the v a l i d i t y and u t i l i t y of v a r i o u s a p p r o a c h e s to the t h e o r e t i c a l p h e n o m e n o l o g i c a l d e s c r i p t i o n of m u l t i c o m ponent diffusion in s o l i d s o l u t i o n s ; 1-5 and 2) to p r o v i d e a r e a l b a s i s f o r p h y s i c a l i n s i g h t into the w a y s in which a t o m i c s p e c i e s i n t e r p e n e t r a t e to e s t a b l i s h diffusion p a t h s f o r a s y s t e m . The i n i t i a l p h a s e of t h i s study f o c u s e d upon the p e n e t r a t i o n b e h a v i o r of the t h r e e t r a c e r s , Cu 67, Ni 66, and Zn 6s in h o m o g e n e o u s c o p p e r r i c h a l l o y s containing up to 30 p c t Ni and Zn. T r a c e r diffusion c o e f f i c i e n t s of Zn 6s h a v e been r e p o r t e d e a r l i e r ; 6 the p r e s e n t p a p e
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