Formation of metastable austenite in splat quenched high alloy steels containing Cr, Mo or W
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Splat Quenched High Alloy Steels Containing Cr, Mo or W
for the F e - C r - C s y s t e m , 1.0 to 2.4 wt pet C and 3 to 22 wt pct Mo for the F e - M o - C s y s t e m and 1.0 to 2.4 wt pct C and 3 to 24 wt pct W for the F e - W - C s y s t e m . T h u s , this a u s t e n i t e f o r m a t i o n r a n g e is m u c h
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T . MINEMURA, A. INOUE, Y. KOJIMA, AND T. MASUMOTO T h e a p p l i c a t i o n of the splat q u e n c h i n g technique to s e v e r a l alloy s t e e l s has been u n d e r t a k e n to i n v e s t i gate quenching effects such as the e x t e n s i o n of solid s o l u b i l i t i e s of c a r b o n and alloying e l e m e n t s , r e f i n e m e n t of g r a i n s i z e and f o r m a t i o n of n o n e q u i l i b r i u m p h a s e s . F u r t h e r m o r e , one e x p e c t s that t h e s e effects may endow the s t e e l s with high s t r e n g t h and good d u c t i l i t y . F r o m this point of view, Inoue el al 1-5 have p e r f o r m e d a s e r i e s of i n v e s t i g a t i o n s on the splat quenching of h i g h - c a r b o n alloy s t e e l s for the last s e v e r a l y e a r s . As a r e s u l t , they have found an a m o r phous phase in the F e - ( C r , Mo, W)-C s y s t e m s 1-s and a m e t a s t a b l e N i ~ l - t y p e compound in the F e - ( N i , Mn)A1-C s y s t e m s , 4 and that t h e s e alloys have high s t r e n g ( h and good d u c t i l i t y . In s u b s e q u e n t i n v e s t i g a t i o n s , the p r e s e n t a u t h o r s have found that a m e t a s t a b l e a u s t e n i t e s i n g l e phase is f o r m e d (instead of the e q u i l i b r i u m f e r r i t e - c a r b i d e m i x t u r e ) in r a p i d l y quenched F e - ( C r , Mo, W)-C a l l o y s c o n t a i n i n g a lower c a r b o n content than those a l l o y s showing the a m o r p h o u s p h a s e . However, it m a y be noted that t h e s e alloy s t e e l s c o n t a i n much higher a m o u n t s of c a r b o n than n o r m a l l y found in alloy s t e e l s . T h e s e a l l o y s p o s s e s s high s t r e n g t h and good d u c t i l i t y . T h i s c o m m u n i c a t i o n d e a l s with the c o m p o s i t i o n r a n g e s in which a u s t e n i t e f o r m s and with the m i c r o 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 of these a u s t e n i t i c a l l o y s . S p e c i m e n s w e r e p r e p a r e d in the f o r m of continuous r i b b o n with 0.03 to 0.05 m m t h i c k n e s s and 2 to 10 mm width by a single r o l l e r - t y p e quenching a p p a r a t u s . The a m o u n t of m e l t e d alloys per r u n was about 1 g and the r o t a t i o n speed of the s t e e l r o l l (200 m m in diam) was c o n t r o l l e d at about 5000 r p m . A s - q u e n c h e d s t r u c t u r e s of the s p e c i m e n s were e x a m i n e d by t r a n s m i s s i o n e l e c t r o n m i c r o s c o p y and X - r a y d i f f r a c t i o n using f i l t e r e d Fe-Kc~ r a d i a t i o n ; The h a r d n e s s and s t r e n g t h of the s p e c i m e n s were m e a s u r e d by a
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