A framework to model thermomechanical coupled of fracture and martensite transformation in austenitic microstructures

A fully thermomechanical coupled phase-field (PF) model is presented to investigate the mechanism of austenite-to-martensite phase transformation (MPT) and crack initiation as well as its propagation in pure austenitic microstructures. The latent heat release and absorption involved in the MPT are explicitly taken into account by coupling the PF model with transient latent heat transfer. In order to consider temperature dependency in the PF model for MPT, a temperature-dependent Landau polynomial function, whose parameters are identified using molecular dynamics (MD) simulations, is proposed. Furthermore, the fracture surface energy is approximated based on the second-order PF model and then, the temporal evolution of the damage variable is given by the variational derivative of the total potential free energy of the system with respect to the damage variable. The achieved numerical results demonstrate that the model can be employed to predict the fracture mechanism of austenitic microstructures under a thermomechanical field in a multiphysics environment. The results reveal that the temperature has a tremendous impact on the growth rate of both martensitic variants and consequently on the crack growth path. The key contributions of this work are to shed light on the impact of thermal boundary conditions on the coupled process of MPT, crack initiation and growth.