Mechanical contributions to the plane-strain deformation and recrystallization textures of aluminum-killed steel

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T h i s w o r k i s c o n c e r n e d with the t e x t u r e ch an g es which u n d e r l i e the r e d u c t i o n dependence of the p l a s t i c a n i s o t r o p y of cold r o l l e d and r e c r y s t a l l i z e d k i l l e d - s t e e l s t r i p . The e a r l i e r o b s e r v a t i o n s of Whiteley and W i s e x on the m a x i m u m in the i n t e n s i t y of r o l l i n g plane { 111} w e r e r e p e a t e d and extended by i n t r o d u c i n g into the c o l d - r e d u c t i o n step the v a r i a b l e of d e f o r m a t i o n - z o n e g e o m e t r y (i.e. A, the r a t i o of the m e a n height of the zone to i t s length). A r a n g e of A < 1 to A = 4 w a s c o v e r e d by cold r o l l i n g (1, s t r a i n and t e x t u r e g r a d i e n t s a p p e a r and the t e x t u r e i n v e r s i o n o c c u r s in the m o r e s t r a i n e d r e g i o n s at s m a l l e r total r e d u c t i o n s - a f t e r a s l i t t l e as 40 pct f o r s u r f a c e l a y e r s with A = 4. The m e c h a n i s m a p p e a r s not to be changed, h o w e v e r , only a c c e l e r a t e d in t e r m s of the i m p o s e d r e d u c t i o n . Implications for practical texture control are discussed.

THE c r y s t a l l o g r a p h i c

t e x t u r e s of w r o u g h t m e t a l s a r e c o m m o n l y c l a s s e d a c c o r d i n g to the p r o c e s s e s by which they a r e p r o d u c e d , e.g. r o l l i n g , w i r e d r a w i n g , deep drawing. 2'3 T h i s i m p l i e s that the s t r a i n s t a t e is defined by the shape change i m p o s e d in p r o c e s s i n g , o r that s t r a i n i n g is h o m o g e n e o u s . In many p r a c t i c a l o p e r a ti o n s the i m p l i c a t i o n is a r e a s o n a b l e one. It can happen, h o w e v e r , that the s t r a i n s ta te i s not fully known f r o m just the e x t e r n a l s h a p e - c h a n g e ; l o c a l v a r iat i o n s a r e p o s s i b l e depending upon the g e o m e t r y of the d e f o r m a t i o n zone in the p r o c e s s i n g s y s t e m . A u s e ful index of that g e o m e t r y is the r a t i o of the m e a n zone t h i c k n e s s , h, to the zone c o n t a c t - l e n g t h , L, or A = h / L , F i g . 1. Many e f f e c t s of p r o c e s s i n g r e s p o n d to change in A. One of i n t e r e s t h e r e is the amount of r ed u n d an t s t r a i n in a g i v en r e d u c t i o n ; t h e r e a r e good t h e o r e t i c a l g r o u n d s 4 for e x p e c t i n g it to i n c r e a s e with A, and e x p e r i m e n t has shown it to be an a p p r o x i m a t e l y s i n g l e v a l u e d and l i n e a r function of A i r r e s p e c t i v e of the p a r t i c u l a r r e d u c t i o n and zone contour, e.g. die a n g l e . 5-7 Strain d i s t r i b u t i o n , a l s o , has been found to be s t r o n g l y dependent on A. 7'8 It s e e m e d r e a s o n a b l e t h e r e f o r e , as a s t a r t i n g point in the p r e s e n t w o r k , to s u p p o s e that t e x t u r e would be s e n s i t i v e to A l e v

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