Compressive strain-induced austenite transformation in 52100 steel
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Compressive Strain-I nduced Austenite Transformation in 52100 Steel C. A . STICKELS AND C. R. P E T E R S In a r e c e n t s t u d y of p l a s t i c d e f o r m a t i o n in quenched and t e m p e r e d 52100 s t e e l , I it was o b s e r v e d that 1) r e t a i n e d a u s t e n i t e i s p r o g r e s s i v e l y t r a n s f o r m e d to m a r t e n s i t e with i n c r e a s i n g a m o u n t s of c o m p r e s s i v e p l a s t i c s t r a i n , and 2) the r e l a t i v e i n t e n s i t y of X - r a y s d i f f r a c t e d f r o m a u s t e n i t e (200) p l a n e s , m e a s u r e d on a p l a n e p e r p e n d i c u l a r to the a x i s of c o m p r e s s i o n , d e c r e a s e s with i n c r e a s i n g s t r a i n m o r e r a p i d l y than d o e s the r e l a t i v e i n t e n s i t y of X - r a y s d i f f r a c t e d f r o m a u s t e n i t e (220) p l a n e s m e a s u r e d on the s a m e p l a n e . T h e l a t t e r b e h a v i o r w a s e x p l a i n e d by noting that the flow s t r e s s of a u s t e n i t e c r y s t a l s with a (200) p l a n e p e r p e n d i c u l a r to the c o m p r e s s i o n a x i s should be l o w e r than the flow s t r e s s of c r y s t a l s with a (220) p l a n e s i m i l a r l y o r i e n t e d , when both a r e c o n s t r a i n e d to d e f o r m with the s a m e s h a p e change a s the bulk m a t e r i a l (s = ey = - e z / 2 , w h e r e z is in the d i r e c t i o n of the c o m p r e s s i o n a x i s ) . T h e s e r e s u l t s w e r e o b t a i n e d f r o m 52100 s t e e l a u s t e n i t i z e d at 840~ o i l quenched and t e m p e r e d at 175~ The r a t e of t r a n s f o r m a t i o n of a u s t e n i t e with t e n s i l e p l a s t i c s t r a i n was m e a s u r e d by A v e r b a c h , et al e on s a m p l e s of 2340 s t e e l u n t e m p e r e d , and t e m p e r e d a t 200, 300 and 400~ (93, 149 and 204~ T h e s e a u t h o r s found that the f r a c t i o n of r e t a i n e d a u s t e n i t e t r a n s f o r m e d by unit p l a s t i c t e n s i l e s t r a i n d e c r e a s e d a s the t e m p e r i n g t e m p e r a t u r e i n c r e a s e d . T h e effect of t e m p e r i n g t e m p e r a t u r e on the r a t e of s t r a i n i n d u c e d t r a n s f o r m a t i o n in c o m p r e s s i o n has a p p a r e n t l y not b e e n s y s t e m a t i c a l l y m e a s u r e d p r e v i ously. C o m p r e s s i o n t e s t s a m p l e s of 52100 s t e e l w e r e m a chined f r o m the s a m e c o m m e r c i a l l y - p r o d u c e d tubing u s e d in e a r l i e r s t u d i e s . / , 3 S p e c i m e n s 3.96 m m d i a m and 5.20 m m height w e r e p r o c e s s e d f i r s t to d e v e l o p a p e a r l i t i c m i e r o s t r u c t u r e , 3 then a u s t e n i t i z e d f o r 15 rain a t 900~ in e v a c u a t e d v y c o r c a p s u l e s , quenched in o i l at 55~ ( b r e a k i n g the c a p s u l e ) , then t e m p e r e d at 100, 125, 150, 175 and 200~ Seven s p e c i m e n s w e r e t e m p e r e d a t e a c h of the l a s t f o u r
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