Microstructural analysis by high-voltage electron diffraction of severely drawn iron wires
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T H E s t r a i n h a r d e n i n g of bce i r o n h z and b i n a r y s u b s t i t u t i o n a l i r o n alloys 3 is s u b s t a n t i a l (about 20,000 to 25,000 psi per unit s t r a i n or 138 to 173 M N / m z p e r unit s t r a i n ) and l i n e a r to the highest t r u e s t r a i n s a t tained.* The (110) wire t e x t u r e and the attendant i n *Truestraine is hereindefinedas In(Do/D)2, whereDoandD are the initial and finaldiamsrespectively. t e r c u r l i n g of the r i b b o n - s h a p e d g r a i n s 4 c l e a r l y play a m a j o r r o l e in this p e r s i s t e n t s t r a i n h a r d e n i n g , but the s t r e n g t h e n i n g effect of the r e s u l t a n t c e l l u l a r s u b s t r u c t u r e is not yet adequately u n d e r s t o o d ; nor has the s t r i k i n g r e f i n e m e n t of the cell s i z e with i n c r e a s ing s t r a i n b e e n fully explained. We have r e p o r t e d a l i n e a r r e l a t i o n s h i p b e t w e e n flow s t r e s s and the r e c i p r o c a l of the t r a n s v e r s e l i n e a r - i n t e r c e p t cell size, ~ and developed a model ~'5 for this dependence in which it was a s s u m e d that the glide d i s l o c a t i o n s do not p e n e t r a t e the cell b o u n d a r i e s . However, Rack and Cohen 2 and Langford e t a l . 3 l a t e r o b s e r v e d that the c e l l u l a r s t r e n g t h e n i n g in v a r i o u s bcc i r o n alloys can be r e duced too much by a l l o y i n g to j u s t i f y this s i m p l e a s s u m p t i o n . Rack and Cohen 6 also found that the s t r e n g t h e n i n g effect of the c e l l s in c o l d - d r a w n and r e c o v e r y - a n n e a l e d i r o n w i r e s changes p r o g r e s s i v e l y f r o m a d -~ to the H a l l - P e t c h d -V2 r e l a t i o n s h i p b e t w e e n the a s - d e f o r m e d and a n n e a l e d conditions. Moreover, GEORGE LANGFORD,formerly with the U.S. Steel Corporation, Monroeville,Pennsylvania,is now with the Chemstrand Research Center. Inc., Monsanto Company, Durham, North Carolina. MORRIS COHEN is Ford Professor of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge Massachusetts, 02139. Part of this paper is based on a doctoral thesis submitted by G. Langord to the Department of Metallurgy and Materials Science at the Massachusetts Institute of Technology in 1966. The research was continued at the U.S. Steel Corporation in Monroeville,Pennsylvania. Manuscript submitted February 4, 1974. METALLURGICALTRANSACTIONSA
our s u b s e q u e n t l y p r o p o s e d m e c h a n i s m of d y n a m i c r e c o v e r y 7 does not take into account the c o n t i n u i n g f o r m a t i o n of new c e l l s v i a the polygonization of c e l l s p l a s t i c a l l y bent by the i n t e r c u r l i n g p r o c e s s , and it does not e x p l a i n how d y n a m i c r e c o v e r y c o u n t e r b a l a n c e s the c e l l u l a r r e f i n e m e n t in fcc m e t a l s (which s t r a i n h a r d e n at a m a r k e d l y d i m i n i s h i n g r a t e ) in cont
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