Multi-phase-field modeling of diffusive solid phase transition in carbon steel during continuous cooling transformation

The growth kinetics and final morphology of ferrite (α)(α) grains are characterized by interfacial energy and boundary mobility, which strongly correlate to constituent phase, misorientation angle and the specific orientation relationship at the α/γα/γ interface, such as the Kurdjumov–Sachs (KS) orientation relationship. In a previous phase-field simulation of the αα grain growth, interfacial energy and mobility is assumed to be constant. Therefore, the simulated morphology of αα grains is equiaxed. In this study, the multi-phase-field (MPF) simulation of αα grain growth during γ→αγ→α transformation is performed to study the effects of phase- and misorientation-dependent interfacial energy and boundary mobility on the growth kinetics of αα grains. The phase and misorientation dependence of interfacial energy is simply described by the Read–Shockley equation. Our results indicate that the phase- and misorientation-dependent interfacial energy induces αα grain growth along the γγ grain boundary so as to reduce the total interfacial energy of the system. Furthermore, by considering both the phase- and misorientation-dependent interfacial energy and boundary mobility, the plausible growth kinetics of αα grains can be reproduced and the morphology of αα grains can be quite similar to the αα grain morphology determined by the KS orientation relationship.