On the short-range order in silver-rich Ag-Cd solid solutions
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The s h o r t - r a n g e o r d e r in A g - C d a l l o y s c o n t a i n i n g 5 to 38 a t . p c t Cd w a s i n v e s t i g a t e d by liquid m e t a l solution c a l o r i m e t r y and e l e c t r i c a l r e s i s t i v i t y m e a s u r e m e n t s . The r e s u l t s i n d i c a t e that the d e g r e e of s h o r t - r a n g e o r d e r in s l o w l y c o o l e d s p e c i m e n s w a s e q u i v a l e n t to e q u i l i b r i u m s h o r t - r a n g e o r d e r at a p p r o x i m a t e l y 450 to 500 K. S p e c i m e n s quenched f r o m v a r i o u s t e m p e r a t u r e s showed the e f f e c t s of h e a t t r e a t m e n t on the d e g r e e of s h o r t r a n g e o r d e r . The e n e r g y e f f e c t s a s s o c i a t e d with s h o r t - r a n g e o r d e r in the c o m p o s i t i o n r a n g e 16 to 38 at. p c t Cd w e r e a p p r o x i m a t e l y 60 to 90 cal p e r g - a t o m . It i s c o n c l u d e d f r o m t h e r e s u l t s that the r e s i s t i v i t y in A g - C d a l l o y s d e c r e a s e s with i n c r e a s i n g d e g r e e of short-range order.
P U B L I S H E D v a l u e s of the h e a t s of f o r m a t i o n s u g g e s t that s h o r t - r a n g e o r d e r o c c u r s in s i l v e r - r i c h A g - C d s o l i d s o l u t i o n a l l o y s . 1-3 A l s o , s o m e f e a t u r e s of t h e i r d e f o r m a t i o n b e h a v i o r have been e x p l a i n e d by the d e s t r u c t i o n of s h o r t - r a n g e o r d e r . 4 S h o r t - r a n g e o r d e r in t h e s e a l l o y s , h o w e v e r , h a s not been i n v e s t i g a t e d s y s tematically. In the w o r k r e p o r t e d h e r e , the e f f e c t s of heat t r e a t m e n t s and c o m p o s i t i o n on t h e s h o r t - r a n g e o r d e r in A g - C d a l l o y s containing f r o m 4.8 to 38.3 a t . p c t Cd w e r e i n v e s t i g a t e d . Changes in the e n e r g y content and e l e c t r i c a l r e s i s t i v i t y , which a r e known to c o r r e l a t e with the d e g r e e of s h o r t - r a n g e o r d e r , w e r e m e a s u r e d in s p e c i m e n s c o o l e d at d i f f e r e n t r a t e s f r o m v a r i o u s temperatures. E X P E R I M E N T A L PROCEDURES P r e p a r a t i o n of S p e c i m e n s A g - C d a l l o y s w e r e p r e p a r e d by m e l t i n g w e i g h e d a m o u n t s of s i l v e r (99.99 p c t p u r e ) and c a d m i u m (99.95 p c t p u r e ) in a g r a p h i t e c r u c i b l e u n d e r m o l t e n p o t a s s i u m c h l o r i d e . The m e l t s w e r e s o l i d i f i e d in the s h a p e of r o d s . The r o d s w e r e s e a l e d in e v a c u a t e d V y c o r t u b e s and h o m o g e n i z e d at 773 K f o r 10 d a y s . A f t e r a s u r f a c e l a y e r ( ~ in.) w a s r e m o v e d b y m a c h i n i n g , t h e r o d s w e r e s w a g e d and d r a w n into w i r e (0.0396 in. d i a m ) with a p p r o p r i a t e i n t e r m e d i a t e a n n e a l s . T h e c o m p o s i t i o n s of the s p e c i m e n s o b t a i n e d by c h e m i c a l a n
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