Molecular dynamics simulation of nucleation and grain growth in Al–7Si alloy under shear flow conditions

Molecular dynamics simulations were conducted to investigate the effects of shear flow on nucleation, grain growth, and crystal growth during the solidification of Al–7Si alloys. Tensile simulations were performed to evaluate the mechanical properties of the solidified alloys. The mean first–passage time method was used to determine nucleation rates and critical nucleus sizes, while curvature-driven growth theory and the Johnson–Mehl–Avrami (JMA) model were applied to analyze grain growth kinetics and crystal growth modes under shear. The results show that as the shear intensity increases, the nucleation rate increases while the critical nucleus radius remains nearly unchanged. Grain growth is accelerated by shear flow, and JMA results reveal a transition from three-dimensional to one-dimensional growth with increasing shear strength. Tensile simulations further demonstrate that, within a certain range, stronger shear flow during solidification improves the yield strength and ductility of the alloy. These findings provide theoretical guidance for tailoring microstructures and enhancing mechanical properties via controlled shear flow.