The development of the deformation texture in zirconium during rolling in sequential passes
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Slip and twinning s y s t e m s a c t i v a t e d by r o l l i n g in s e q u e n t i a l p a s s e s were o b s e r v e d on a c o a r s e g r a i n e d z i r c o n i u m p o l y c r y s t a l . At l e a s t five independent d e f o r m a t i o n modes a r e activated; slip and twinning s y s t e m s o c c u r s i m u l t a n e o u s l y . F o r low d e g r e e s of d e f o r m a tion the m a i n slip s y s t e m is p r i s m slip {1010}(12i0), e v e n when the o r i e n t a t i o n is not f a v o r a b l e . The l a t t i c e r o t a t i o n s caused by slip p r o c e e d g r a d u a l l y with i n c r e a s i n g deformation; they a r e r e l a t i v e l y s m a l l although the s t r a i n achieved can be l a r g e . On the other hand, twinning c a u s e s spontaneous, l a r g e - s c a l e l a t t i c e r o t a t i o n s , even for low d e g r e e s of d e f o r m a t i o n . The type of twinning depends l a r g e l y on the c r y s t a l l o g r a p h i c o r i e n t a t i o n of the m a t r i x . F o r b a s a l pole o r i e n t a t i o n s of the u n d e f o r m e d g r a i n s in the a r e a 0 to 50 deg f r o m the n o r m a l d i r e c t i o n {1122} twinning b e c o m e s p r e f e r e n t i a l l y o p e r a t i v e . F o r b a s a l pole o r i e n t a t i o n s of the u n d e f o r m e d g r a i n s in the a r e a 50 to 90 deg f r o m the n o r m a l d i r e c t i o n , however, {10i2} twinning b e c o m e s p r e f e r e n t i a l l y o p e r a t i v e . In both o r i e n t a t i o n a r e a s as a c o m p l e m e n t a r y s y s t e m {1121} twinning is o p e r a t i v e . F o r a l l d e f o r m a t i o n s y s t e m s t h e i r o p e r a t i o n is independent of the a z i m u t a l p o s i t i o n of the b a s a l pole in these a r e a s . The lattice r o t a t i o n s a l t e r the o r i e n t a t i o n of the c r y s t a l l i t e s in such a way that the b a s a l poles a l l become aligned m o r e o r l e s s in the d i r e c t i o n of the d e f o r m i n g c o m p r e s sive force. F o r higher d e g r e e s of d e f o r m a t i o n p y r a m i d a l slip with a (c + a) type B u r g e r s V e c t o r can e x p l a i n why this p r e f e r r e d o r i e n t a t i o n is m a i n t a i n e d as f i n a l position, which for z i r c o n i u m shows a split of b a s a l poles of • to 50 deg towards the t r a n s v e r s e d i r e c tion. The method of following the c o m p l i c a t e d i n t e r a c t i o n s between different slip and twinning s y s t e m s in a stepwise d e f o r m e d , c o a r s e g r a i n e d sheet by 1) t r a c e a n a l y s i s of the d e f o r m a t i o n modes, 2) by c o r r e s p o n d i n g l y d e r i v e d lattice r o t a t i o n s , and 3) by t e x t u r e m e a s u r e m e n t s leads to an e x p l a n a t i o n of the t e x t u r e d e v e l o p m e n t in z i r c o n i u m . It is d i s c u s s e d on the b a s i s of b a s a l pole r o t a t i o n s .
T H E t h e o r i e s about the d e v e l o p m e n t of d e f o r m a t i o n t e x t u r e s ~'~ have b e e
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