Dual slip in germanium under compression
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DUAL s l i p , w h i c h i s
s l i p i n t w o g l i d e d i r e c t i o n s on a s i n g l e set o f p a r a l l e l g l i d e p l a n e s , was s t u d i e d in t h e work r e p o r t e d here f o r two main r e a s o n s . F i r s t , s t u d ies o f dual slip in s i n g l e c r y s t a l s o f s e v e r a l m a t e r i a l s ~-3 h a v e y i e l d e d d i f f e r e n t c l a s s e s o f r e s u l t s w h e n c o m p a r e d to o n e a n o t h e r a n d w h e n c o n t r a s t e d to s i n g l e slip r e s u l t s . H e n c e , in a n e f f o r t to r e s o l v e d i s t i n c t i o n s b e t w e e n t h e c l a s s e s , t h e d e t e r m i n a t i o n o f dual slip characteristics was a p p r o p r i a t e in a c a s e w h e r e dual slip was f a v o r e d in u n c o n s t r a i n e d d e f o r m a t i o n a n d c o u l d be e x a m i n e d e l e c t r o n - m i c r o s c o p i c a l l y w i t h o u t further dislocation m o t i o n . Second, t h e r e c o v e r y of dual-slipped c r y s t a l s should p r o d u c e hexagonal n e t w o r k s w h o s e configurations s h o u l d provide a test for g r a i n b o u n d a r y t h e o r i e s . 4-7 T h e f i r s t a s p e c t o f t h e r e s e a r c h is d i s c u s s e d in t h e p r e s e n t p a p e r ; t h e s e c o n d , in a l a t e r o n e . P r i o r w o r k on d u a l s l i p y i e l d e d s t r e s s - s t r a i n c u r v e s o f t h e type d e p i c t e d i n F i g . 1 . T h e c u r v e s of s e t A w e r e obtained for zinc a (hcp) and anthracene 2 (monoc l i n i c ) . In b o t h c a s e s s t a g e I o f w o r k h a r d e n i n g w a s a t t e n u a t e d f o r the d u a l s l i p o r i e n t a t i o n a n d r a p i d s t a g e II h a r d e n i n g w a s o b s e r v e d ; t h e s e f i n d i n g s w e r e r a t i o n a l i z e d in t e r m s of t h e i n t e r a c t i o n o f t h e t w o o p e r ative glide s y s t e m s producing network dislocation locks. T h i s i n t e r p r e t a t i o n i s r e a s o n a b l e s i n c e s l i p in b o t h c r y s t a l s t e n d s t o be r e s t r i c t e d t o t h e b a s a l p l a n e i ) b e c a u s e the relatively low e n e r g y of stacking f a u l t s o n t h e s e p l a n e s f a v o r s d i s s o c i a t i o n into p a r t i a l d i s l o c a t i o n s a n d i i ) b e c a u s e of a r e l a t i v e l y h i g h P e i e r l s f o r c e r e s i s t i n g glide on p l a n e s of o t h e r crystallographic s e t s . 1'2'8 T h e r e a r e s e v e r a l d e t a i l e d m e c h a n i s m s w h i c h h a v e t h e p r o p o s e d 1'2 f o r m of l o c k s f o r t h e d u a l s l i p o r i e n t a t i o n a n d w h i c h a c t in a d d i t i o n t o t h e u s u a l l o c k i n g , d i p o l e f o r m a t i o n , a n d so f o r t h , a p p l i c a b l e i n a s i n g l e s l i p o r i e n t a t i o n .9 S e v e r a l o f t h e s e m e c h a n i s m s a r e i l l u s t r a t e d in Fig. 2 . F o r t h e c a s e o f r e p u l s i v e interaction between perfect dislocations, t h e r e a r e
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