合金定向凝固一次枝晶间距模拟

Simulation of primary dendrite spacing in unidirectionally solidified alloy

建立二元合金树枝晶生长的二维元胞自动机模型,模拟丁二腈2.5%(质量分数)乙醇定向凝固枝晶生长和一次枝晶间距选择过程。模拟结果表明:在给定的凝固条件下,定向凝固一次枝晶间距可在一个范围内变化,其具体取值与凝固历史具有相关性。在相同的温度梯度和不同冷却速度下,模拟给出的一次枝晶间距上、下限与实验结果吻合较好,详细分析影响定向凝固一次枝晶间距上下限的因素。结果表明:在给定凝固条件和合金系条件下,液相中无对流,影响一次枝晶间距上下限的主要因素是界面能和溶质扩散系数。

A two-dimensional cellular automaton model for simulation of dendritic growth during solidification of binary alloy was built. The microstructural evolution in a directionally solidified succinonitile-2.5% （mass fraction） ethanol alloy was simulated. The results show that the primary dendrite spacing may vary in a range under a given solidification condition. Its value depends on the solidification history of the sample. The calculated upper and lower limits of primary dendrite spacing at different cooling rates are in good agreement with the experimental results. The effect factors of the solidification history dependence of the primary dendritic spacing were analyzed in detail. It indicates that the interracial energy and the solute diffusion coefficients are the main factors if there is no convection in the liquid phase.