Isothermal studies of bainitic and martensitic transformations in some low alloy steels
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agent in the cutting. T h e c o l l e c t e d p o w d e r s w e r e then e n c a p s u l a t e d s e p a r a t e l y in p l a s t i c v i a l s and a n n e a l e d at 100~ by i m m e r s i n g the v i a l s in b o i l i n g w a t e r for 40 min to r e v e r s e the m a r t e n s i t e t r a n s f o r m a t i o n 8 induced by cutting. A P i c k e r 8668A d i f f r a c t o m e t e r with CoK~ r a d i a t i o n was u s e d f o r XRD e x a m i n a t i o n . The s c a n n i n g s p e e d was 30~ p e r h. The r e s u l t i n g p a t t e r n s f o r the two c o m p o s i t i o n a l l o y s a r e shown in F i g . 3. The p o w d e r p a t t e r n f r o m the h y p o e u t e c t o i d a l loy showed c l e a r l y that the p a t t e r n is c o n t r i b u t e d by two p h a s e s . One p h a s e had a f c c s t r u c t u r a l p a t t e r n with a l a t t i c e p a r a m e t e r of 3.67A. T h i s c o r r e s p o n d s to the c~ p h a s e . T h e o t h e r p h a s e had a C s C 1 s t r u c t u r a l p a t t e r n with a p a r a m e t e r of 2.94,~. T h i s c o r r e s ponds to t h e / 3 ' p h a s e . The X - r a y r e f l e c t i o n s f r o m the c~ phase did not h a v e the s h a r p n e s s and c l e a r n e s s in c o m p a r i s o n with the r e f l e c t i o n s f r o m t h e / 3 ' p h a s e . T h i s is the r e s u l t of t h e / 3 ' phase g e n e r a l l y tending to r e a c h e q u i l i b r i u m m o r e quickly than the ~ p h a s e in s t r e s s r e l i e f a n n e a l i n g . ~ The powder p a t t e r n f r o m the e u t e c t o i d a l l o y showed only one phase, a CsC1 s t r u c t u r a l p a t t e r n with a l a t t i c e p a r a m e t e r of 2.95A. T h i s c o r r e s p o n d s to t h e / 3 ' p h a s e . The l a t t i c e p a r a m e t e r a g r e e s w e l l with the X - r a y r e s u l t s of Rao and A n a n t h a r a m a n . ~ T h e s e X - r a y r e s u l t s c o n f i r m the m e t a l l o g r a p h i c o b s e r v a t i o n s , v i z only c~ i n / 3 ' in the hypoeutectoid alloy a n d / 3 ' in the e u t e c t o i d a l l o y . They a l s o indicate that no s i g n i f i c a n t d e z i n c i f i c a t i o n o c c u r r e d d u r i n g the long annealing. No e v i d e n c e of a e u t e c t o i d r e a c t i o n r e p o r t e d by Shinoda and A m a n o was d e t e c t e d in the p r e s e n t work. T h e w o r k of M a s s a l s k i and Kittl 6 on the ~ / ( ~ +/3) phase boundary and the w o r k of Rao and A n a n t h a r a man S on both ~/(c~ +/3) and (a +/3)//3 p h a s e bounda r i e s a l s o f a i l e d to d e t e c t any e v i d e n c e of e u t e c t o i d r e a c t i o n . Hence it is b e l i e v e d that the s u p p o s e d f3' e u t e c t o i d r e a c t i o n d o e s not e x i s t . The w r i t e r s thank A m p c o Metal, D i v i s i o n of A m p c o P i t t s b u r g h C o r p o r a t i o n f o r the c h e m i c a l a n a l y s i s of the a l l o y s .
1. G. Shinodaand Y. Amano:Jap. Inst. Metals, 1960,vol. 1, pp. 54-57. 2. F. A. Shunk and R. P. Elliot:Constitution of Binary Alloys, first suppl
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