X-ray diffraction study of a bulk, polycrystalline Ag-9 at. pct Sn alloy deformed in compression
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c o m p l e t e study of the b r o a d e n i n g and shifts in p o s i tion of X - r a y diffraction peaks is a u s e f u l n o n d e s t r u c tive t e c h n i q u e for s y s t e m a t i c a l l y e v a l u a t i n g the effect of p l a s t i c d e f o r m a t i o n on the m i c r o s t r u c t u r e of bulk m a t e r i a l . F r o m the b r o a d e n i n g of powder p a t t e r n peaks ~-s one can d e t e r m i n e the effective p a r t i c l e size De(hkl) which c o n t a i n s the t r u e s i z e of 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 D(h/el) and a f i c t i t i o u s size due to faulting i n the c r y s t a l s , as well a s the e l a s t i c s t r a i n s p r o d u c e d by d i s l o c a t i o n s . F r o m r e l a t i v e d e v i a t i o n s in the p o s i t i o n s of the powder p a t t e r n peaks of cold worked m e t a l s and a l l o y s one can d e t e r m i n e the l a t t i c e s t r e s s e s in the s a m p l e , 4-6 the amount of faulting, and the c h a n g e s in l a t t i c e p a r a m e t e r due to the p r e s e n c e of d i s l o c a t i o n s or the r e d i s t r i b u t i o n of the c h e m i c a l s p e c i e s within the material. 7 The l a t t i c e s t r e s s e s from applied or r e s i d u a l f o r c e s p r e s e n t in the d e f o r m e d m a t e r i a l a r e a c t u a l l y detected as m a c r o s t r a i n s p r o d u c i n g a s y s t e m a t i c p a t t e r n of changes in the p o s i t i o n s of the powder peaks. The m a g nitude of t h e s e changes in l a t t i c e s p a c i n g Ad/d (equal to the l a t t i c e p a r a m e t e r change Aa/a in cubic c r y s tals) 4'8 d e p e n d s on the acting s t r e s s e s and on the r e l a tive o r i e n t a t i o n as well as type of the d i f f r a c t i n g l a t t i c e p l a n e s (hkl) in e l a s t i c a l l y a n i s o t r o p i c m a t e r i a l s . Stacking f a u l t s on (111) p l a n e s in fcc m e t a l s will also c a u s e c h a r a c t e r i s t i c changes in peak p o s i t i o n s 8 which m i g h t be s i m i l a r for s o m e (h/el) r e f l e c t i o n s to those p r o d u c e d by m a c r o s t r e s s e s . 2'6 R e s o l u t i o n of peak p o s i t i o n data when s t a c k i n g faults and l a t t i c e s t r e s s e s act s i m u l t a n e o u s l y r e q u i r e s the a n a l y s i s of the r e l a t i v e changes between i n d i v i d u a l peak p o s i t i o n s (such as 111, 222, 200, and 400) which r e p r e s e n t two s e t s of m u l t i p l e o r d e r r e f l e c t i o n s . 2'6 P r o c e s s e s which d e c r e a s e the effective p a r t i c l e s i z e De(h/el) or i n c r e a s e the e l a s t i c m i c r o s t r a i n s c a u s e R. P. I. ADLER, formerly Graduate Student, Yale University, New Haven, Conn., is Group Leader, Brunswick Corp., Needham Laboratories, Needham, Mass. C. N. J. WAGNER, formerly Associate Professor, Department of Engineeringand Applied Science, Yale University, New Haven; Conn., is Professor, Materials Department, University of California, Los Angeles,
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