Recrystallization following hot-working of a high-strength low-alloy (HSLA) steel and a 304 stainless steel at the tempe
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L. A. JACKMAN,
AND
W.J.
CHILDS
The r e c o v e r y and r e c r y s t a l l i z a t i o n b e h a v i o r of two c o m m e r c i a l q u a l i t y s t e e l s , a Cb(Nb) s t r e n g t h e n e d h i g h - s t r e n g t h l o w - a l l o y (HSLA) s t e e l and a 304 s t a i n l e s s s t e e l , w a s s t u d i e d following h o t - w o r k i n g . S p e c i m e n s w e r e d e f o r m e d in t e n s i o n at a c o n s t a n t head v e l o c i t y of 2 i n . / s to r e d u c t i o n s - i n - a r e a of 30 to 50 pct at t e m p e r a t u r e s in t h e a u s t e n i t e r a n g e f r o m 1600 ~ to 1900~ T h e s u b s e q u e n t a n n e a l i n g b e h a v i o r w a s o b s e r v e d a t the t e m p e r a t u r e of d e f o r m a t i o n . D e c r e a s i n g r e c r y s t a l l i z a t i o n r a t e s with d e c r e a s i n g t e m p e r a t u r e a n d / o r d e f o r m a t i o n w e r e o b s e r v e d . It i s s u g g e s t e d that CbC p r e c i p i t a t i o n o c c u r r e d d u r i n g a n n e a l i n g of t h e HSLA s t e e l and a c c o u n t e d f o r an a r r e s t in t h e s o f t e n i n g b e h a v i o r . F o r the 304 s t a i n l e s s s t e e l it i s concluded that dyna~aic r e c r y s t a l l i z a t i o n t o o k p l a c e d u r i n g d e f o r m a t i o n , that t h e r m a l m i c r o t w i n n i n g w a s an a c t i v e r e c o v e r y m e c h a n i s m d u r i n g a n n e a l i n g , and that t h e r e was a preference for grain boundaries as nucleation sites for recrystallized grains. These c o n c l u s i o n s r e g a r d i n g the a n n e a l i n g b e h a v i o r of 304 s t a i n l e s s s t e e l w e r e s u p p o r t e d by m e t a l l o g r a p h i c a n a l y s i s of s p e c i m e n s w a t e r quenched f r o m the t e m p e r a t u r e of d e f o r m a t i o n .
DURINGt h e
p l a s t i c d e f o r m a t i o n of m e t a l s t h e r e a r e c h a n g e s in s u b s t r u c t u r e and m i c r o s t r u c t u r e which a r e w e l l d o c u m e n t e d and which depend upon m a n y v a r i a b l e s . 1'2 One of the p r i m a r y v a r i a b l e s i s the t e m p e r a t u r e a t which t h e m e t a l i s d e f o r m e d , giving r i s e to two b r o a d d i v i s i o n s t e r m e d h o t - and c o l d - w o r k i n g . The b a s i c a s p e c t s of t h e s e two f o r m s of d e f o r m a t i o n have b e e n defined by m a n y , o t h e r i n v e s t i g a t o r s . ''3-7 I n d e p e n d e n t of w h e t h e r t h e m e t a l i s d e f o r m e d by h o t - o r c o l d - w o r k i n g , when h e l d at e l e v a t e d t e m p e r a t u r e s , following }leformation, t h e m e t a l will u n d e r g o s t r u c t u r a l c h a n g e s tending to r e t u r n it to the u n d e f o r m e d condition. The two b a s i c s o f t e n i n g p r o c e s s e s a r e r e c o v e r y x'5-9 and r e c r y s t a l l i z a t i o n , l ' s ' 7 , l ~ Byrne 1 has summarized the m e c h a n i s m s of r e c o v e r y a s a function of the a n n e a l i n g t e m p e r a t u r e . He i n d i c a
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