X-ray studies of cold-worked ternary alloys containing Pd-Ag-Au
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o f the c o h e r e n t l y d i f f r a c t i n g d o m a i n s a n d s t r a i n s w i t h in t h e s e d o m a i n s . X - r a y s t u d i e s a r e especially s u i t able to s t u d y t h e c o l d - w o r k e d s t r u c t u r e r e s u l t i n g f r o m h e a v y d e f o r m a t i o n . The e f f e c t s w h i c h r e s u l t f r o m d e f o r m a t i o n c a n i n f l u e n c e t h e p o s i t i o n a s w e l l a s the s h a p e of each reflection. Deformation stacking faults g i v e rise to a s y m m e t r i c a l b r o a d e n i n g a n d a shift in t h e p o s i t i o n of the X - r a y r e f l e c t i o n s , w h e r e a s t w i n faults produce asymmetrical broadening and a n e g l i g i b l e p e a k s h i f t . In a d d i t i o n t o t h e b r o a d e n i n g due t o faulting, cold-work p r o d u c e s broadening as a r e s u l t o f s m a l l domain size a n d distortions within each domain. S A M P L E P R E P A R A T I O N AND E X P E R I M E N T A L PROCEDURES H i g h p u r i t y P d (99.97 p c t ) , A g ( 9 9 . 9 9 p c t ) , a n d A u ( 9 9 . 9 7 p c t ) p o w d e r s s u p p l i e d by E n g e l h a r d I n d u s t r i e s , I n c . w e r e u s e d f o r p r e p a r i n g the s a m p l e s . S m a l l c o m p a c t s made f r o m well m i x e d p o w d e r s o f t h e p r o p e r c o m p o s i t i o n s were m e l t e d in a n i n d u c t i o n f u r n a c e u n d e r a h y d r o g e n a t m o s p h e r e . T h i s p r o c e d u r e did not l e a d to a s i g n i f i c a n t w e i g h t l o s s . The r e s u l t a n t i n g o t s w e r e d e f o r m e d in d i f f e r e n t d i r e c t i o n s t o p r o m o t e h o m o g e n i z a t i o n , a n d s e a l e d in e v a c u a t e d q u a r t z t u b e s , a f t e r f l u s h i n g t h r e e t i m e s w i t h a r g o n gas. They were t h e n h o m o g e n i z e d for a w e e k at 9 0 0 ° C . All s a m p l e s w e r e c o l d - w o r k e d at r o o m t e m p e r a t u r e b y filing f r o m h o m o g e n i z e d s o l i d s . F o r the P d - A u a n d P d - A g - A u a l l o y s filings of less t h a n 3 2 5 m e s h w e r e filled into the c a v i t y of a n a l u m i n u m s a m p l e h o l d e r and parlodion was used as a binder. The standard s p e c i m e n u s e d for the S t o k e s c o r r e c t i o n s w a s p r e p a r e d f r o m well a n n e a l e d t u n g s t e n p o w d e r . T h e r e m a i n i n g solid s a m p l e s were mechanically polished after def o r m i n g slightly by pressing and subsequently annealed for 2 4 h r at 8 5 0 ° C . T h i s p r o c e d u r e led to s a m p l e s w h i c h g a v e r e p r o d u c i b l e lattice p a r a m e t e r s a f t e r s u c c e s s i v e l y l o a d i n g a n d r e l o a d i n g the s p e c i m e n into the d i f f r a c t o m e t e r . C o n s e q u e n t l y , s a m p l e r o t a t i o n w a s not VOLUME 2 , JANUARY 1971 -309
n e c e s s a r y . S p e c i m e n s of P d - A g a l l o y s w e r e p r e p a r e d i n t h e f o r m of b r i q u e t t e s by p r e s s i n g t
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