A modified phase-field model for grain boundary migration in sintering

Regulating temperature and pressure during spark plasma sintering is crucial for optimizing the grain structure and performance of AZ91D magnesium alloys, with grain boundary migration being a critical factor in this process. To address the lack of models that simultaneously consider thermal and mechanical driving forces, this study develops a novel entropy-based non-isothermal phase-field model. The model uniquely couples applied stress with rigid body motion, significantly increasing the initial particle velocity by up to four times compared to traditional approaches. Additionally, the model incorporates temperature evolution through the heat conduction equation and introduces adaptive boundary conditions along with a shared orientation field approach, achieving a computational efficiency improvement of at least 4.6 times in large-scale simulations. Through systematic analysis of grain boundary migration under varying temperature gradients and applied stresses, a critical threshold for sintering parameters is identified: beyond a temperature gradient of 0.3T₀ and an applied stress of 50 MPa, further increases do not significantly enhance sintering efficiency. This work provides a comprehensive framework for understanding and optimizing sintering processes, offering new insights into the coupled effects of thermal and mechanical driving forces on grain boundary dynamics.