DIRECT MEASUREMENT OF LENGTH CHANGES IN (225) MARTENSITE HABIT PLANE

The lengths of lines in the (225)F martensite habit plane of an Fe-Cr-C alloy have been compared with the corresponding lengths in austenite before transformation, by the use of dimensionally stable replicas of the untransformed austenite. The measurements show that the change in length of such lines is certainly less than 0.2% and is probably zero. In particular no significant changes in length were observed for lines parallel to [1 1 ̄0]F even though the transformation of [1 1 ̄0]F into [11 1 ̄]B involves a reduction in interatomic distance of 1.8%. These results are not consistent with theories involving either a uniform dilatation or a non-uniform strain in the habit plane but they do support the plastic accommodation model proposed by Bowles and Dunne. © 1969.