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Fig. 3--Slip lines on iron deformed 10 pct in compression at -78 C.

Structure of Beta-Brass Single Crystals After Steady-State Creep

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A) The s p a c i n g of slip b a n d s r e m a i n s v i r t u a l l y constant as s t r a i n i n c r e a s e s B) Both the d i s p l a c e m e n t per slip b a n d and the width of the band i n c r e a s e with i n c r e a s i n g s t r a i n . The local s t r a i n per slip band ( d i s p l a c e m e n t / w i d t h ) also tends to i n c r e a s e with i n c r e a s i n g s t r a i n C) At low s t r a i n s , the s t r a i n a c c o u n t e d for by the slip bands ( d i s p l a c e m e n t / s p a c i n g ) is about equal to the total s t r a i n . At higher s t r a i n s (10 to 20 pct) only about half the total s t r a i n i s c o n c e n t r a t e d in the m a j o r slip b a n d s . The p i c t u r e that r e s u l t s from these m e a s u r e m e n t s is not too different f r o m that p r o p o s e d e a r l i e r . 2 The slip b a n d s that f o r m v e r y e a r l y in the s t r a i n i n g p r o c e s s r e m a i n active throughout d e f o r m a t i o n . However, these b a n d s w o r k - h a r d e n to the extent that glide d i s l o c a t i o n s e v e n t u a l l y r e q u i r e other paths to a c c o m p l i s h d e f o r m a tion. The region b e t w e e n active slip b a n d s a p p a r e n t l y b e c o m e s filled f a i r l y u n i f o r m l y at higher s t r a i n s , as is e v i d e n c e d by the fine slip l i n e s in Fig. 1. At low t e m p e r a t u r e s , the slip b a n d s a r e m o r e diff u s e . They tend to be c o m p o s e d of fine s u b b a n d s , Fig. 3. M e a s u r e m e n t of d i s p l a c e m e n t by e i t h e r t e c h nique b e c o m e s quite difficult. However, some r e s u l t s were obtained both at - 7 8 ~ and -196~ At these t e m p e r a t u r e s the offset per b a n d is on the o r d e r 10 to 20 pct of the room t e m p e r a t u r e v a l u e , a n d the a v e r a g e s p a c i n g is ~