中文摘要：

采用相场方法研究了液相扩散系数对 Al356.1合金凝固过程初晶（Al）相显微组织演变的影响。在相场模拟中，采用了两套液相扩散系数，而其他热物理参数和数值参数则保持一致。第一套液相扩散系数只考虑随温度变化的 Arrhenius 类型的杂质扩散系数，而第二套则为随温度和成分变化的精准的液相原子移动性数据库。对于第二套液相扩散系数，还分析了扩散系数矩阵中的非对角项对Al356.1合金凝固过程中显微组织演变的影响。通过相场模拟发现：在3种液相扩散系数情况下，初晶（Al）相的形貌、枝晶尖端的速率和枝晶前端的成分曲线均有不同。研究结果表明：精确的液相原子移动性参数对定量模拟凝固过程显微组织演变是非常重要的。

英文摘要：

（The effect of liquid diffusion coefficients on the microstructure evolution during solidification of primary （Al） phase in Al356.1 alloy was investigated by means of the phase-field simulation using two sets of diffusion coefficients in liquid phase, while fixing other thermophysical and numerical parameters. The first set is only with impurity coefficients of liquid phase in Arrhenius formula representing only the temperature dependence. While the second set is with the well-established atomic mobility database representing both temperature and concentration dependence. For the second set of liquid diffusion coefficients, the effect of non-diagonal diffusion coefficients on the microstructure evolution in Al356.1 alloy during solidification was also analyzed. The differences were observed in the morphology, tip velocity and composition profile ahead of the tip of the dendrite due to the three cases of liquid diffusivities. The simulation results indicate that accurate databases of mobilities in the liquid phase are highly needed for the quantitative simulation of microstructural evolution during solidification.