Orientation relationships in the recrystallization of polycrystalline, hexagonal metals
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ROLF RIXEN
T h e i d e a l o r i e n t a t i o n s o c c u r r i n g in the r e c r y s t a l l i z a t i o n t e x t u r e s of p o l y c r y s t a l l i n e z i r c o n i u m and t i t a n i u m a r e c o m p a r e d with the p r e f e r r e d o r i e n t a t i o n s found in g r o w t h s e l e c t i o n e x p e r i m e n t s on s i n g l e c r y s t a l s of z i n c and c a d m i u m . It i s found that the i d e a l o r i e n t a t i o n s a r i s i n g on the r e c r y s t a l l i z a t i o n of the p o l y c r y s t a l l i n e m e t a l s lie b e t w e e n the s i n g l e c r y s t a l p r e f e r r e d o r i e n t a t i o n s and c a n v e r y w e l l be i n t e r p r e t e d a s c o m p r o m i s e t e x t u r e s . With t h i s c o n c e p t and the a s s u m p t i o n that the r e c r y s t a l l i z a t i o n n u c l e i a r e o r i g i n a l l y p a r t of the d e f o r m e d m a t r i x , s l i g h t v a r i a t i o n s in the t e x t u r e s a r i s i n g f r o m d i f f e r e n t a n n e a l i n g t i m e s and t e m p e r a t u r e s c a n a l s o be e x p l a i n e d .
ACCORDING
to B e c k , x the r e c r y s t a l l i z a t i o n t e x t u r e s in m e t a l s a r e m o s t l y c a u s e d by s e l e c t i v e g r o w t h of recrystallization nuclei, which originally may have possessed a more or less random orientation distribution. T h a t s u c h a g r o w t h s e l e c t i o n r e a l l y t a k e s p l a c e h a s so f a r b e e n d e m o n s t r a t e d m a i n l y b y m e a n s of s i n g l e c r y s t a l e x p e r i m e n t s , lbe and Lficke,2 f o r e x a m p l e , a l l o w e d a l a r g e n u m b e r of n u c l e i f o r m e d by high l o c a l d e f o r m a t i o n to g r o w into a l e s s s t r o n g l y d e f o r m e d s i n g l e c r y s t a l . It w a s found t h a t one of the n u c l e u s c r y s t a l s u s u a l l y g r e w in p r e f e r e n c e to the o t h e r s until it f i n a l l y o c c u p i e d the w h o l e c r o s s - s e c t i o n of the s p e c i m e n , and that t h e s e d o m i n a n t n u c l e u s c r y s t a l s had q u i t e d e f i n i t e o r i e n t a t i o n r e l a t i o n s h i p s to the d e f o r m e d s i n g l e c r y s t a l m a t r i x . F r o m t h i s it h a s b e e n c o n c l u d e d that n u c l e i w i t h s u c h o r i e n t a t i o n s h a v e a l a r g e r g r o w t h r a t e than the o t h e r s . It is not p o s s i b l e , h o w e v e r , to a p p l y the r e s u l t s of s u c h i n v e s t i g a t i o n s on s i n g l e c r y s t a l s d i r e c t l y to the f o r m a t i o n of r e c r y s t a l l i z a t i o n t e x t u r e s in p o l y c r y s t a l l i n e m a t e r i a l . W h i l e the m a t r i x c o n s i s t s of a s i n g l e o r i e n t a t i o n in the c a s e of a s i n g l e c r y s t a l , p o l y c r y s talline material possesses a deformation texture w h i c h is u s u a l l y c o m p o s e d of s e v e r a l c o m p o n e n t s . A s l o n g a s the s e l e c t i v e g r o w t h p r o c e s s t a k e s p l a
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