On the microstructure of extruded rods and drawn wires of beryllium
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two s l i p m o d e s a p p r o a c h i n g each o t h e r n e a r 500~ 4 In addition, s l i p on p y r a m i d a l p l a n e s with c +a s l i p v e c t o r s has a l s o b e e n o b s e r v e d at high t e m p e r a t u r e s , s'6 T h e r e f o r e s o m e c o m b i n a t i o n s of t h e s e d e f o r m a t i o n m o d e s m u s t be r e s p o n s i b l e f o r the i n i t i a l f i b e r t e x t u r e f o r m a t i o n . Once t h e y have r e a c h e d the (1010) f i b e r o r i e n t a t i o n , t h e s e t e x t u r e d g r a i n s m u s t of c o u r s e c o n tinue to d e f o r m with continued e x t r u s i o n . It is p r o posed, t h e r e f o r e , that the c u r l y g r a i n s t r u c t u r e d e v e l ops m a i n l y a f t e r the (1010) f i b e r o r i e n t a t i o n has b e e n reached. Fig. 2 g i v e s the c r y s t a l l o g r a p h i c d e t a i l s of a c r y s t a l o r i e n t e d with the [10i0] d i r e c t i o n aligned in the e x t r u sion d i r e c t i o n . To extend the c r y s t a l in [1010] d u r i n g continued e x t r u s i o n , b a s a l slip is i n e f f e c t i v e as it c o n t r i b u t e s no e x t e n s i o n in [10~0]. L i k e w i s e , (1012) t w i n ning is i n e f f e c t i v e as its o p e r a t i o n would s h o r t e n the c r y s t a l in [10i0]. The a l t e r n a t i v e is f o r p r i s m o r p y r a m i d a l (c +a) s l i p which can act f a v o r a b l y to p r o d u c e the d e s i r e d e x t e n s i o n . Since p r i s m s l i p is the e a s i e r of the two, it is a s s u m e d h e r e . The two a c t i v e slip s y s t e m s a r e (0110) [2110] and (1100) [[120] as shown in F i g . 2. L e t t i n g x - [1010], y - [1210] and z -= [0001]
On the Microstructure of Extruded Rods and Drawn Wires of Beryllium G. Y. CHIN D u r i n g a l i t e r a t u r e s u r v e y the author c a m e a c r o s s a p h o t o m i c r o g r a p h of an e x t r u d e d Be rod, which has the hcp s t r u c t u r e , in a p a p e r by Kaufmann e t a l . ~ This m i c r o g r a p h is r e p r o d u c e d in Fig. 1. In the longitudinal s e c t i o n (b), the g r a i n s a r e e l o n g a t e d as would be e x p e c t e d f r o m the e x t r u s i o n . In the t r a n s v e r s e s e c t i o n (a), h o w e v e r , the g r a i n s a p p e a r r i b b o n - s h a p e d and c u r l e d around one a n o t h e r . Such a m i c r o g r a p h is r e m i n i s c e n t of t h o s e of d r a w n w i r e s of b c c m e t a l s such as W and F e f i r s t r e p o r t e d by P e c k and T h o m a s . 2 The e x planation t h e r e was given by H o s f o r d s in t e r m s of the t e n d e n c y f o r plane s t r a i n d e f o r m a t i o n of g r a i n s when e x t e n d e d o r c o m p r e s s e d in a (110) d i r e c t i o n . Drawn w i r e s of b c c m e t a l s and c o m p r e s s e d d i s k s of fcc m e t als exhibit a (110) f i b e r t e x t u r e . H o s f o r d showed that 50 pct l e s s slip is r e q u i r e d if a (110) c r y s t a l d e f o r m s by plane s t r a i n i n s t e a d of a x i
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