Slip-band displacements in iron
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Fig. 1--Slip lines on iron d e f o r m e d 20 pct in c o m p r e s s i o n at room t e m p e r a t u r e .
Slip-Band Displacements in Iron A. R . R O S E N F I E L D AND G. T . HAHN
EXPERIMENTAL d e t e r m i n a t i o n of slip o f f s e t s is n e c e s s a r y f o r the q u a n t i t a t i v e d e v e l o p m e n t of r e a l i s t i c m o d e l s of p l a s t i c f l o w . S i n c e t r a n s m i s s i o n e l e c t r o n m i c r o s c o p y d o e s not l e n d i t s e l f t o t h i s k i n d of m e a s u r e m e n t , we h a v e e m p l o y e d s u r f a c e r e p l i c a t i o n . With t h i s t e c h n i q u e , two m e t h o d s a r e a v a i l a b l e f o r m e a s uring displacements across a slip band: a) " U p " d i s p l a c e m e n t s * c a n b e m e a s u r e d f r o m the *"Up" and "down" displacementsrefer to the direction of the surface offsets relative to the shadowingdirection.
Fig. 2----Slip lines on iron d e f o r m e d 10 pct in c o m p r e s s i o n at room t e m p e r a t u r e .
Table I. Characteristic Dimensions of Slip Bands in Iron
Temperature, ~ 25
f o r e s h o r t e n i n g of s h a d o w s c a s t b y s m a l l l a t e x b a l l s , a t e c h n i q u e due o r i g i n a l l y to F e n g , 1 F i g . 1. b) " D o w n " d i s p l a c e m e n t s a p p e a r a s w h i t e l i n e s , w h e r e the s h a d o w i n g m a t e r i a l h a s n o t b e e n d e p o s i t e d , F i g . 2. In t h i s c a s e , the d i s p l a c e m e n t i s f o u n d to b e w t a n 0, w h e r e w i s t h e w i d t h of the w h i t e l i n e a n d 8 is the s h a d o w i n g angle. B o t h m e t h o d s h a v e b e e n u s e d to e x a m i n e t h e d i s p l a c e m e n t s w i t h i n s l i p b a n d s in c o a r s e g r a i n e d i r o n t e s t e d in c o m p r e s s i o n a t s l o w s t r a i n r a t e . A d d i t i o n a l d a t a a r e o b t a i n e d f r o m d i r e c t m e a s u r e m e n t s of t h e s p a c i n g of s l i p b a n d s a n d t h e i r w i d t h s (the w i d t h s of t h e b l a c k l i n e s in F i g . 1 - - " u p " d i s p l a c e m e n t s - - a r e A. R. ROSENFIELD and G. T. HAHN are Associate Chief and Chief, respectively, Metal Science Group, Battelle Memorial Institute, Columbus, Ohio. Manuscript submitted December 9, 1969. 1080-VOLUME 1,APRIL 1970
-78 -196
Strain, Pct 1 ~3 10 20
Slip Band Width,# 0.08-+0.015 0.10-+0.05 0.12-+0.07 0.21 -+0.07
Slip Band Depth,/1 0.014-+0.003 0.06 -+0.04 0.06 -+0.01 0.19 -+0.06
10 20
-
0.010 -+0.005 0.020 + 0.009
20
-
0.017 -+0.005
Spacing,# 1.75-+0.25 1.6 -+0.2 2.1 -+0.8 1.7 -+0.7 -
a l s o the w i d t h s of t h e s l i p b a n d s . T h e s e s h o u l d b e c o r r e c t e d for m a t e r i a l buildup, but this has not b e e n d o n e h e r e s i n c e no g r e a t i m p r o v e m e n t i n a c c u r a c y w o u l d r e s u l t ) . T h e e x p e r i m e n t a l d a t a a r e g i v e n in T a b l e I. S i n c e t h e s l i p b a n d s in i r o n a r e q u i t e n o n u n i f o r m , t h e r e i s q u i t e a l a r g e a m o u n
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