Martensite crystal lattice, mechanism of austenite-martensite transformation and behavior of carbon atoms in martensite
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NEARLYfifty y e a r s
ago (1926) it was found by F i n kand C a m p b e l l 1 in the USA and by Seljakov, K u r d j u m o v and Gudzov e in the USSR, that m a r t e n s i t e had a body c e n t e r e d t e t r a g o n a l l a t t i c e with the p a r a m e t e r s n e a r to the c~-iron l a t t i c e . Two y e a r s l a t e r t h e r e has been e s t a b l i s h e d 3 the l i n e a r d e p e n d e n c e of " c " and " a " p a r a m e t e r s a s well as c/a of m a r t e n s i t e l a t t i c e upon the C c o n c e n t r a t i o n in s t e e l . Both facts, the c o n c e n t r a t i o n d e p e n d e n c e of p a r a m e t e r s and the t e t r a g o n a l i t y b e c a m e the m o s t i m p o r t a n t e x p e r i m e n t a l proofs of the notion on the n a t u r e of m a r t e n s i t e , a s a s u p e r s a t u r a t e d s o l i d s o l u t i o n of c a r bon i n v~-iron with c a r b o n a t o m s in o c t a h e d r a l i n t e r s t i c e s in rows p a r a l l e l [001]. The s t r i c t c o r r e s p o n d e n c e between the a x i a l r a t i o c//a and c a r b o n content in the i n i t i a l a u s t e n i t e t o g e t h e r with s t r i c t o r i e n t a t i o n r e l a t i o n s h i p s 4,s b e t w e e n a u s t e n i t e and m a r t e n s i t e l a t t i c e s w e r e the m o s t i m p o r t a n t e x p e r i m e n t a l proofs of the notion about m e c h a n i s m of A ~ M transformation as a diffusionless regular r e a r r a n g e m e n t of T to ~ - l a t t i c e . 4~z L i n e a r d e p e n d e n c e of m a r t e n s i t e l a t t i c e p a r a m e t e r s " v " and " a " upon c a r b o n content can be e x p r e s s e d C = a~)+otp;
a = a~ - / 3 p ;
[1]
c/a = 1 + yp w h e r e ao - F e ~ l a t t i c e p a r a m e t e r ~ = 0.116 • 0.002: /3 = 0.013 + 0.002; ~ = 0.046 • 0.001. T h e s e r e l a t i o n s w e r e c o n f i r m e d by n u m e r o u s i n v e s G V. KURDJUMOVis Director, Institute of Metallography and Metal Physics, I. P, Bardln Scmntific Research Institute for Ferrous Metallurgy, Moscow, U.S.S,R., member of the Academy of Sclence~of the U.S.S R.; Fellow of the MetallurgicalSociety of AIME. This material was the basis for a series of seminars in the Umted States m the spring of 1975 and is a critical review of Dr. Kurdjumov's recent research on martens~te,including new Russian work. The author's td~omatic text has been retained. Manuscript submitted January 15, 1976. METALLURGICALTRANSACTIONSA
t i g a t i o n s 8,9 i n the p e r i o d of 1 9 2 8 - 1962, and found to be a p p l i c a b l e for alloyed s t e e l s too. 1~ T h e n u m e r i c a l v a l u e s of c o e f f i c i e n t s c~ and/3 allowed d e t e r m i n i n g the local s t r a i n s c a u s e d by c a r b o n a t o m s i n s - i r o n l a t t i c e and w e r e used by Z e n e r 1~ and Khac h a t u r y a n 13 in t h e i r o r d e r - d i s o r d e r t h e o r i e s in m a r t e n s i t e and for the c a l c u l a t i o n of c r i t i c a l t r a n s i t i o n t e m p e r a t u r e f r o m t e t r a g o n a l to cubic m a r t
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