Examination in three principal sections of the dislocation substructures in heavily cold-rolled 70/30 brass

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Examination in Three Principal Sections of the Dislocation Substructures in Heavily Cold-Rolled 7 0 / 3 0 Brass D. M . T U R L E Y THE d i s l o c a t i o n s u b s t r u c t u r e s p r o d u c e d in c o l d r o l l e d 7 0 / 3 0 b r a s s h a v e b e e n p r e v i o u s l y e x a m i n e d in t h e electron microscope u s i n g thin film techniques. 1 T h e thin f i l m s w e r e t a k e n f r o m a p l a n e p a r a l l e l t o t h e rolling plane, a n d at high reductions two distinct t y p e s o f dislocation s u b s t r u c t u r e s were o b s e r v e d . T h e interpretation o f t h e s e s u b s t r u c t u r e s however w a s diffic u l t . S e l e c t e d a r e a d i f f r a c t i o n i n d i c a t e d that o n e t y p e of s u b s t r u c t u r e consisted of s u b g r a i n s and the other o f f i n e d e f o r m a t i o n t w i n s w h i c h lie in t h e r o l l i n g p l a n e . T h e electron m i c r o g r a p h s corresponding t o t h e s e diff r a c t i o n p a t t e r n s h o w e v e r did not s h o w n o r m a l subg r a i n o r d e f o r m a t i o n twin s t r u c t u r e s . R e c e n t work o n c o l d - r o l l e d s t e e l2'3 a n d c o p p e r4 h a s s h o w n t h a t subg r a i n s t r u c t u r e s a r e s e e n m o r e c l e a r l y in t h e e l e c t r o n m i c r o s c o p e w h e n t h e y a r e v i e w e d in t h e t r a n s v e r s e and longitudinal sections. T h e p u r p o s e of t h e p r e s e n t w o r k was t h e r e f o r e t o d e t e r m i n e w h e t h e r e x a m i n a t i o n o f c o l d - r o l l e d 7 0 / 3 0 b r a s s in t h e t r a n s v e r s e a n d l o n gitudinal s e c t i o n s w o u l d aid in t h e i n t e r p r e t a t i o n o f t h e s u b s t r u c t u r e s p r e v i o u s l y o b s e r v e d in t h e r o l l i n g p l a n e . A n a n n e a l e d b a r o f b r a s s a p p r o x i m a t e l y ~- m . d e e p by 1 i n . wide by 4 i n . l o n g w a s c o l d - r o l l e d u n i d i r e c 1

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D. M . TURLEY is Experimental Officer, Australian Defence Scientific Service, Department of Supply, Defence Standards Laboratories, Melbourne, Australia. Manuscript submitted March 1 5 , 1971. VOLUME 2 , NOVEMBER 1971-3233

Fig. 1--Electron m i c r o g r a p h taken in the longitudinal s e c t i o n s h o w i n g that w e l l - d e v e l o p e d s u b g r a i n s a r e p r e s e n t .

t i o n a l l y , t a k i n g s m a l l r e d u c t i o n s p e r p a s s , down to a thickness of 0.0055 in. T o p r e p a r e thin f i l m s from t h e t r a n s v e r s e and longitudinal sections t h e thickness o f t h e r o l l e d s t r i p w a s i n c r e a s e d by c o p p e r p l a t i n g . C o m p o s i t e s p e c i m e n s o f c o p p e r a n d b r a s s 3 m m in diam a n d a p p r o x i m a t e l y 0 . 0 0 8 i n . t h i c k were t h e n taken from the r e q u i r e d section and thinned electrolyrically in a P T F E h o l d e r . E x a m i n a t i o n o f thin f i l m s t a k e n f r o m t h e t r a n s v e r s e and longitudinal section