溶质相互作用对Al-3Cu-1Mg合金枝晶组织的影响

Effects of the Solute Interaction on Dendritic Growth in Al-Cu-Mg Alloy

应用三维元胞自动机模型模拟了Al-3Cu-1Mg合金的树枝晶组织,研究了溶质互扩散对枝晶组织的影响。采用两种方式处理溶质扩散系数:(1)溶质扩散系数与溶质成分和温度有关,不考虑溶质互扩散系数;(2)耦合计算溶质扩散矩阵,即考虑溶质互扩散的影响。结果表明,枝晶尖端选择参数比边缘稳定性理论给出的值小。由于Al-Cu-Mg体系中两种合金元素的相互吸引作用,在溶质互扩散时,枝晶尖端生长速度较小,而尖端半径较大。

The dendritic growth of an Al-3Cu-1Mg alloy was calculated using a three-dimensional cellular automaton model.Effects of the off-diagonal terms of the solute diffusion coefficient matrix on the dendritic growth during solidification of the alloy were investigated.The solute diffusion coefficients were treated in two ways：（1）by considering the concentration-dependent and temperature-dependent diffusion,and neglecting the effect of solute interactions or the off-diagonal terms of the diffusion matrix,or（2）by calculating the diffusion coefficients by solving the full diffusion matrix.The results indicate that the calculated dendrite tip selection parameter is the smaller than that obtained using the marginal stability criterion.When the off-diagonal terms of the solute diffusion coefficient matrix are considered,the growth velocity of the dendrite tip is decreased,while the dendrite tip radius is increased as a result of the attraction of the solutes in the Al-Cu-Mg system.