The effect of quench-aging on inhomogeneous yielding of steels with very low interstitial solute content
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S E V E R A L o b s e r v a t i o n s on the effects of quenching and quench aging on the m e c h a n i c a l p r o p e r t i e s of i r o n s 1-4 and s t e e l s 5 of low i n t e r s t i t i a l - s o l u t e content have been r e p o r t e d . Quenching these m a t e r i a l s f r o m a high t e m p e r a t u r e such as 700~ g r e a t l y s u p p r e s s e s or e l i m i n a t e s the i n h o m o g e n e o u s y i e l d i n g b e h a v i o r c h a r a c t e r i s t i c of r e c r y s t a l l i z e d and slowly cooled m a t e r i a l . Quenching r e s u l t s in a s u b s t a n t i a l r e d u c tion of the H a l l - P e t c h g r a i n s i z e - y i e l d s t r e s s p a r a m e t e r ky. Low t e m p e r a t u r e aging of quenched m a t e r i a l , 140~ or lower, r e s u l t s in an i n c r e a s e d L ~ d e r ' s s t r a i n , lower yield s t r e s s , and ky value. While some of this work has r e c o g n i z e d that d i s l o c a t i o n s a r e i n t r o d u c e d by the t h e r m a l s t r e s s e s on q u e n c h i n g , the role of these d i s l o c a t i o n s in the m e c h a n i c a l r e s p o n s e after quench aging has not r e c e i v e d adequate a t t e n t i o n , and the a u t h o r is not a w a r e of any s y s t e m a t i c study r e l a t i n g d i s l o c a t i o n s t r u c t u r e and m e c h a n i c a l p r o p e r t i e s in quench aging these m a t e r i a l s . Wilson s'6 p r o p o s e s that i n h o m o g e n e o u s y i e l d ing, and the ky v a l u e , in quenched and aged m a t e r i a l l a r g e l y depends on i n t e r s t i t i a l solute s e g r e g a t i o n at g r a i n b o u n d a r i e s . C o t t r e l l 2 and F i s h e r 3 d i s c u s s quench aging m e c h a n i c a l p r o p e r t y r e s p o n s e s in t e r m s of "weak and s t r o n g p i n n i n g " effects and the r e l a t i v e r o l e s of u n p i n n i n g of d i s l o c a t i o n s and the a t h e r m a l g e n e r a t i o n of d i s l o c a t i o n s at g r a i n b o u n d a r i e s . They do not state e x p l i c i t l y why the quenched condition r e p r e s e n t s a case of " w e a k p i n n i n g " , whether it be lack of a t m o s p h e r e f o r m a t i o n a r o u n d e x i s t i n g d i s l o c a t i o n s on t h e r m o d y n a m i c g r o u n d s b e c a u s e of a quench f r o m a high t e m p e r a t u r e , or whether it be b e c a u s e of the p r e s e n c e of mobile d i s l o c a t i o n s g e n e r a t e d by quenching s t r e s s e s . The work r e p o r t e d h e r e d e a l s p r i m a r i l y with quench aging of m a t e r i a l of low i n t e r s t i t i a l - s o l u t e content where a range of quenching and aging t e m p e r a t u r e s R. E. HOOK is Senior Research Metallurgist, Research Center, Armco Steel Corporation, Middletown, Ohio. Manuscript submitted June 12, 1969. METALLURGICALTRANSACTIONS
a r e e x a m i n e d and where the d i s l o c a t i o n s t r u c t u r e s a r e o b s e r v e d and r e l a t e d to the m e c h a n i c a l p r o p e r t i e s measured. EXPERIM
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