The room temperature annealing kinetics of stacking faults in cold worked alpha brasses
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f a u l t s in m e t a l s w e r e f i r s t d e t e c t e d b e c a u s e of t h e i r e f f e c t s on X - r a y d i f f r a c t i o n p a t t e r n s . ~ A d e t a i l e d t h e o r y for the d i f f r a c t i o n e f f e c t s of growth f a u l t s was g i v e n b y W i l s o n . 2 All s u b s e q u e n t X - r a y w o r k s-5 is a d e v e l o p m e n t of W i l s o n ' s a p p r o a c h , in which the f a u l t s a r e a s s u m e d to b e d i s t r i b u t e d at r a n dom on a s e t of c l o s e - p a c k e d p l a n e s . An e x t e n s i v e r e v i e w of t h i s s u b j e c t h a s b e e n given b y W a r r e n 6 and only the p e r t i n e n t equation which r e l a t e s the s t a c k i n g fault p r o b a b i l i t y to the p e a k p o s i t i o n s will b e u s e d in t h i s paper. Rudee and Huggins 7 p e r f o r m e d a v e r y c a r e f u l s t u d y of the i s o t h e r m a l r o o m t e m p e r a t u r e a n n e a l i n g of Cu22.7 Zn a l l o y b y X - r a y d i f f r a c t i o n and e l e c t r i c a l r e s i s t i v i t y t e c h n i q u e s . T h e s e a u t h o r s o b s e r v e d that d u r i n g the f i r s t h o u r , the s t a c k i n g fault p r o b a b i l i t y showed an i n c r e a s e of about o n e - q u a r t e r . T h e i r e l e c t r i c a l r e s i s t i v i t y d a t a i n d i c a t e d that an i n c r e a s e in d i s l o c a t i o n length was v e r y u n l i k e l y . They c o n c l u d e d that the i n c r e a s e in the width of the s t a c k i n g f a u l t s was c a u s e d b y s e g r e g a t i o n of the z i n c to the f a u l t s . Rudee and Huggins 7 a l s o found a c o m p l e t e l y u n e x p e c t e d d e c r e a s e in the s t a c k i n g f a u l t p r o b a b i l i t y , at, b y a f a c t o r of two b e t w e e n 27 and 38 h of r o o m t e m p e r a t u r e annealing. T h e y w e r e unable to e x p l a i n the o r i g i n of t h i s sudden d r o p in a . H o w e v e r , t h e y s u c c e s s f u l l y u t i l i z e d the c o r r e l a t i o n of a and the r e s i s t i v i t y d a t a d u r i n g the a b r u p t change to c a l c u l a t e a v a l u e for the s p e c i f i c r e s i s t i v i t y of a s t a c k i n g fault. In the p r e s e n t i n v e s t i g a t i o n , in o r d e r to e l u c i d a t e t h e above m e n t i o n e d a n o m a l o u s b e h a v i o r , a s e r i e s of i s o t h e r m a l r o o m t e m p e r a t u r e (RT) a n n e a l i n g e x p e r i m e n t s was c a r r i e d out on Cu-10 Zn, Cu-20 Zn, and Cu-30 Zn a l l o y s . It w a s o b s e r v e d t h a t a l l t h r e e a l l o y s i n d i c a t e v e r y d i f f e r e n t and d i s t i n c t b e h a v i o r a s f a r a s the s t a c k ing fault p r o b a b i l i t y is c o n c e r n e d . TARIK 6. OGURTANI is Professor of Materials Science and Chairman of Metallurgical Engineering Department, Middle East Technical University, Ankara, Turkey. Manuscript submitted April 18, 1974. METALLURGICAL TRANSACTIONS A
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