Effect of martensite embryo potency on the martensitic transformations in steels—A 3D phase-field study

Abstract

Nucleation during martensitic transformation (MT) has received considerable theoretical attention as it is a complex and rapid process that makes it difficult to study in situ. Earlier theoretical studies indicate that there exists a critical size of the embryo, dependent on the temperature, below which no nucleation would occur. Acquiring knowledge of the critical size and shape of the martensite embryo through simulated MT might yield a better understanding of some of the martensite nucleation aspects. In the present work phase-field method is employed to determine the critical size and shape parameters of the martensite embryo. 3D phase field simulations with pre-existing embryo of spherical as well as ellipsoidal shapes are performed by considering physical parameters corresponding to Fe–C alloys. The results indicate that the potency of martensite embryo affects the MT and also that an ellipsoidal embryo is the most favorable shape, which supports the earlier studies on martensite nucleation. Dislocation density also plays a major role in determining the embryo potency.