Plastic flow in binary substitutional alloys of BCC iron-effects of wire drawing and alloy content on work hardening and
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SOBER, AND W. C. LESLIE
The s t r e n g t h of c o l d - d r a w n , t i t a n i u m - g e t t e r e d i r o n w i r e s can be s u b s t a n t i a l l y i n c r e a s e d by s u b s t i t u t i o n a l s o l u t e s . F o r the e l e m e n t s studied, s t r e n g t h e n i n g is p r o g r e s s i v e l y l e s s in the o r d e r Si, Pt, Mn, Ni, Cr, and Co. The s t r e n g t h e n i n g effect of the solute i n c r e a s e s with s t r a i n , but at a g r e a t l y d i m i n i s h i n g r a t e for t r u e s t r a i n s g r e a t e r than unity. Six at. pct Si r e d u c e s the s t r a i n n e c e s s a r y to a c h i e v e a t e n s i l e s t r e n g t h of 200,000 p s i (1380 M N / m 2) f r o m 7.3 for i r o n to 3.7. T h i s effect of a l l o y i n g on s t r a i n h a r d e n i n g a p p e a r s to be r e l a t e d to the s t r e n g t h of the a n n e a l e d alloy r a t h e r than to the specific a l l o y i n g e l e m e n t used to a c h i e v e that s t r e n g t h . A l s o , the r e d u c t i o n - o f - a r e a ductility of the drawn w i r e s i s m o r e c l o s e l y r e l a t e d to the t e n s i l e s t r e n g t h of the w i r e than to its alloy content or d e g r e e of cold work. A f i b r o u s c e l l u l a r s u b s t r u c t u r e i s f o r m e d in all the a l l o y s , but the f o r m a t i o n of t h e s e c e l l s i s d i s p l a c e d to h i g h e r s t r a i n s , the g r e a t e r the s t r e n g t h e n i n g effect of the solute. The t r a n s i t i o n f r o m h o m o g e n e o u s l y d i s t r i b u t e d , tangled d i s l o c a t i o n s to a c e l l u l a r s u b s t r u c t u r e h a s no effect on the r a t e of s t r a i n h a r d e n i n g of the a l l o y - - a l l o y i n g can be u s e d effect i v e l y a s a s u b s t i t u t e for cold work without a d v e r s e l y affecting the r e s i s t a n c e of the alloy to d u c t i l e f a i l u r e . T H E cost of d r a w n w i r e can be s u b s t a n t i a l l y l o w e r e d by r e d u c i n g the total s t r a i n n e c e s s a r y to a c h i e v e the d e s i r e d s t r e n g t h . However, other r e q u i r e m e n t s such a s r e s i s t a n c e to d u c t i l e f a i l u r e o r to f a i l u r e by fatigue m a y a l s o have to be m e t . P r e v i o u s work 1 has shown that the effects of s u b s t i t u t i o n a l a l l o y i n g e l e m e n t s on the t o u g h n e s s of i n t e r s t i t i a l - f r e e i r o n do not c o r r e l a t e with t h e i r effects on the s t r a i n - r a t e s e n s i t i v i t y and t e m p e r a t u r e d e p e n d e n c e of the flow s t r e s s . That is, e l e m e n t s which a r e s t r o n g solid-solution strengtheners may either i n c r e a s e or d e c r e a s e the d u c t i l e - b r i t t l e t r a n s i t i o n t e m p e r a t u r e . H e r e i n we extend this work to d e t e r m i n e the effects of s o l u t e s on the r a t e of work h a r d e n i n g of a i r o n and to a s c e r t a i n w h e t h e r t h e r e is a c o r r e l a t i o n b e t w e e n s o
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