A study on the kinetics of non-isothermal martensitic transformation considering strain relaxation and thermo-mechanical coupling

Martensite is a key microstructure in high-strength alloy steels, and accurate modeling of its phase transformation is critical for predicting macroscopic deformation and controlling quenching distortion. To investigate microstructural evolution and provide kinetic parameters for quenching simulations, a temperature-dependent elastoplastic phase-field model was developed by extending microelasticity theory to include plastic strain evolution, grain boundary misfit, and coupling with transient heat conduction. Simulations of non-isothermal conditions considered both self- and plastic accommodation mechanisms. The phase transformation kinetics were calibrated using thermal simulation experiments for improved accuracy. Based on the calibrated model, the transformation-induced plasticity (TRIP) mechanism and kinetic evolution under mechanical loading were analyzed. Results show that plastic accommodation relieves local stress via strain relaxation, accelerating transformation and releasing more latent heat, which raises localized temperatures and delays transformation kinetics. Under applied loading, TRIP is dominated by the Magee mechanism, with martensite exhibiting preferred orientation and stress-induced plasticity. A critical threshold exists between the martensite start ( ) temperature and load intensity: below this threshold, the temperature increases with load, while above it, the increase saturates. This work clarifies the stress–transformation coupling mechanism, supporting microstructure control and the design of multi-scale quenching models with accurate kinetic predictions.