The Observation of the Martensite-Like Shear Diffusionless α→γ Transformation in Carbon Steels with Pearlitic Structure

The structure of eutectoid carbon steel with the initially pearlitic structure was studied by transmission electron microscopy and electron diffraction after laser heating. It is shown that, under ultrarapid laser heating, the α-γ phase transformation can proceed by a shear-type diffusionless mechanism that results in the deformation of cementite platelets. The crystallographic characteristics of shear planes involved in the α-γ transformation are determined. Austenite formation was found to occur through the diffusionless shear mechanism, with orientation relationships close to those of Kurdjumov-Sachs

A kinetic model of lath martensite formation

A kinetic theory of martensite formation is developed for the case when isothermal transformation does not complete, which is conventionally explained in terms of the change in the state of $\gamma$ phase. The closest agreement with experiment is obtained when the Kaufman-Cohen theory modifie by Borgenstam and Hillert is used for the nucleation rate