Recovery of ni and ni- co single crystals after varying amounts of cold work
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1. I N T R O D U C T I O N R E C O V E R Y p r o c e s s e s in p o l y c r y s t a l l i n e m e t a l s h a v e been shown t o influence s t r e s s r e l i e f a n d p r e f e r r e d g r a i n boundary migration d u r i n g t h e r m a l treatment. T h e n a t u r e of t h e d e f o r m a t i o n s t r u c t u r e i n e a c h g r a i n i n t h e a g g r e g a t e s e e m s t o be d e c i s i v e i n d e t e r m i n i n g w h i c h g r a i n s will r e c r y s t a l l i z e a n d w h i c h o n e s will r e c o v e r a n d g r o w . a'2 T h u s a r e c o v e r y s t u d y o f o n e g r a i n which has undergone well-characterized deformation w i l l h e l p t o e x p l a i n t h e t h e r m a l s t a b i l i t y of s p e c i f i c d e f o r m e d microstructures. To this purpose the d e f o r m a t i o n a n d r e c o v e r y b e h a v i o r of m u l t i p l e s l i p o r i e n t e d crystals are ideally suited. T h e i r characteristics c a n be s u m m a r i z e d f r o m r e c e n t s t u d i e s on [001] c o p p e r crystals as follows:3-~ i) T h e s h e a r s t r e s s - s h e a r s t r a i n ( z - y ) c u r v e i s n o n l i n e a r a n d i s m a d e up o f s t a g e I I a n d s t a g e III r e g i o n s . S i n c e m a n y e q u i v a l e n t s l i p s y s t e m s o p e r a t e e q u a l l y (8 f o r t h e [001] o r i e n t a t i o n ) , r a p i d h a r d e n i n g i s i n i t i a t e d at yielding a n d t h e orientation r e m a i n s s t a b l e d u r i n g further deformation. ii) A p o w e r l a w f i t t o s t a g e I I r e s u l t s i n a w o r k h a r d e n i n g c o e f f i c i e n t (n) i n the r a n g e 0 . 8 t o 0 . 9 . i i i ) T h e d i s l o c a t i o n d e n s i t y (N) c o r r e l a t e s w i t h t h e s h e a r s t r e s s in t h e u s u a l l i n e a r l o g N - l o g r p l o t . iv) T h e a s - d e f o r m e d d i s l o c a t i o n a r r a y m a n i f e s t s a r a t h e r homogeneous diffuse c e l l u l a r s t r u c t u r e . v ) R e c o v e r y s t u d i e s s h o w that d e f o r m a t i o n p r o d u c t s a r e c o m p r i s e d of d i s l o c a t i o n s , p o i n t d e f e c t s , p o i n t d e fect c l u s t e r s and dislocation loops. iv) R o o m t e m p e r a t u r e d e f o r m a t i o n of c o p p e r i n s t a g e tI generates p r i m a r i l y monopole dislocations w h i c h a n n e a l a b o v e 0 . 6 of t h e a b s o l u t e m e l t i n g t e m p e r a t u r e (Tin) a n d t h i s a n n e a l i n g r a n g e i s d e s i g n a t e d r e g i o n I I . G. VAN DRUNEN is Research Engineer, Chalk River Nuclear Laboratories, Atomic Energy of Canada Ltd., Chalk River, Ontario, Canada, K0J 1J0 and S. SAIMOTO is Professor, Metallurgical Engineering Department, Queen's University, Kingston, Ontario, Canada, K7L 3N6. This paper is basedon a presentation made at a symposium on "Recovery Recrystallization and Grain Growth in Materials" held at the Chicago meeting ofThe Metallurgical Society of AIME, October 1977,under the sponsorship of the Physical Metallurgy Committee. METALLURGICAL
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