Abstract: Based on the phase field model of martensitic phase transformation in Fe-Ni alloys, an elastic-plastic phase field model coupling applied load and plastic deformation is established. The martensitic phase transformation behaviour in Fe-Ni polycrystalline alloys under different loading conditions is simulated, and the growth of variant nuclei, stress distribution and volume fraction during the phase transformation process are analyzed and discussed. During the simulation process, the simulation results are compared with relevant experiments to ensure the reasonableness of the phase field model. The simulation results showed that, in the nucleation growth process, the nucleation points of the phase transformations under the applied tensile load are more than those under the compressive load and the no-load state. The stresses in this process are mainly concentrated at the phase interface between different variants, while the stresses inside the variants are small. An applied tensile load increases the volume fraction in the phase transition and accelerates the kinetic process of the martensitic phase transition, while an applied compressive load provides the opposite effect. The load component perpendicular to the plane of inertia reduces the total free energy of the system for tensile loads compared to compressive loads, and the martensitic phase transformation is more likely to occur under tensile than compressive conditions.

Key words: martensitic phase transformation, phase-field simulation, polycrystals, applied load