基于宏微观耦合三维模型的铝合金凝固模拟

Solidification Simulation of Aluminum Alloy Based on Coupled Macro-micro Three-dimensional Model

采用一种宏微观耦合模型对铝合金的凝固情况进行了模拟。该模型结合了元胞自动机法与有限差分法,与传统的元胞自动机模型不同,该模型不仅考虑了温度场扩散而且考虑了固-液相中的溶质扩散、曲率过冷等因素。枝晶尖端生长速度与局部过冷度的关系采用KGT(Kurz-Giovanola-Trivedi)模型,温度场和浓度场计算采用有限差分法。模型中采用大小两套网格分别进行宏观温度场和微观组织演变的计算,极大地提高了计算效率。利用该模型模拟了铝合金微观多晶生长,以及铝合金在金属模具中的凝固情况,获得了3种不同浇注温度下典型的柱状晶向等轴晶转变的三维图形。

Solidification process of aluminum alloy was simulated by a macro-micro coupled model.The model coupled the finite differential method and cellular automaton method.Different from conventional cellular automaton model,the model considered not only temperature field diffusion but also solute diffusion in liquid and solid state as well as curvature undercooling.The relationship between the dendrite tip growth velocity and local undercooling were calculated based on KGT(Kurz-Giovanola-Trivedi) model,and temperature field and solute filed were calculated by FDM.In the macro-micro model,two kinds of grids were adopted to calculate macro-temperature field and microstructure evolution,greatly improving calculation efficiency.Micro-grain growth in the aluminum alloy and solidification of the alloy in permanent mold were simulated by the model,obtaining typical morphology of columnar grain transformed into equiaxed one in the alloy at three kinds of pouring temperatures.