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合金凝固过程中存在于枝晶尖端液相区的强制对流和自然对流均能改变溶质扩散层厚度,从而会对枝晶形貌产生较大影响.在元胞自动机模型基础上,耦合液体流动方程、热传导方程和溶质对流扩散方程,建立了新的计算微观组织演化的数值模型,并利用该模型研究了强制对流和自然对流对枝晶生长的影响.三维数值模拟结果再现了强制对流作用下等轴枝晶的生长过程,揭示了强制对流对枝晶生长速率和尖端半径的影响特点.同时利用该模型模拟了NH4Cl-H2O溶液定向凝固过程中自然对流对柱状晶生长的影响,并采用相应的实验进行验证.模拟结果与实验结果符合良好,从而证明该模型是可靠的,可推广到实际合金系中.
Forced convection and natural convection existing in the liquid phase of the dendrites during the solidification of the alloy can change the thickness of the solute diffusion layer and thus have a great influence on the dendritic morphology.Based on the cellular automata model, the coupled liquid flow Equation, heat conduction equation and solute convection-diffusion equation, a new numerical model for calculating microstructure evolution was established, and the effects of forced convection and natural convection on the dendrite growth were studied.The results of three-dimensional numerical simulation reproduced the effects of forced convection The effects of forced convection on the growth rate and tip radius of dendrite were revealed.At the same time, the model was used to simulate the effect of natural convection on the columnar crystal growth during directional solidification of NH4Cl-H2O solution, The simulation results are in good agreement with the experimental results, which proves that the model is reliable and can be extended to the actual alloy system.