凝固路径对Al-4.5%Cu合金显微偏析参数影响的数值模拟

Simulation on influence of solidification path on microsegregation parameters in Al-4.5%Cu alloy

通过对Al 4 5%Cu合金铸锭显微偏析形成的数值模拟, 研究了凝固路径对凝固后铸锭不同位置处显微偏析参数的影响。在显微偏析模型中考虑了树枝晶粗化、固相溶质逆扩散、枝晶尖端过冷、随温度变化的溶质扩散系数等影响显微偏析形成的动力学因素。数值方法中采用变网格技术跟踪移动界面, 通过迭代求解溶质扩散方程和溶质守恒方程计算显微偏析参数。结果表明, 对于Al Cu合金, 固相扩散主要由溶质扩散速率控制, 而非局部凝固时间。显微偏析参数不仅取决于局部凝固时间, 还要考虑凝固路径的影响。

Effects of solidification path on microsegregation parameters after solidification at different locations in the ingot of Al-4.5%Cu alloy were studied by microsegregation forming simulation. The main kinetic effects that can influence microsegregation were accounted for in the modeling including secondary arm coarsening, solid-state back diffusion, primary tip undercooling and variable diffusion coefficients according to temperature. Deforming grids technology was applied for tracking the moving interfaces, iterative method was applied for resolving diffusion equation and solute balance equation. The simulation indicates that solid-state diffusion is controlled mainly by the solute diffusing velocity but not the local solidification time for Al-Cu system studied, and the microsegregation parameters are affected not only by local solidification time but also by solidification path.