CA-LBM模型模拟自然对流作用下Al-4.7%Cu合金的枝晶生长

Simulation of Dendritic Growth of Al-4.7%Cu Solid Solution Alloy With the Cellular Automaton and Lattice Boltzmann Method

建立耦合温度场、流场、溶质场的CA-LBM(元胞自动机格子玻尔兹曼方法)数值模型模拟了Al-4.7%Cu固溶体合金的凝固过程。模拟结果再现了自然对流条件下单个枝晶、多个枝晶的生长以及柱状晶向等轴晶转变过程。研究结果表明,自然对流对单个枝晶形貌有明显的影响,使枝晶生长非对称化,即迎流方向的枝晶生长得到促进,顺流方向的枝晶生长受到抑制。对铸锭CET过程的计算表明,自然对流促进温度均匀化,在凝固过程中等温线弯曲程度先增大后减小。另外,自然对流加速了凝固进程,并有细化晶粒的作用。CA-LBM模型再现了自然对流条件下柱状晶的竞争生长、柱状晶向等轴晶的转变以及溶质的晶界偏析。

A numerical model combining CA（Cellular Automaton） and LBM（Lattice Boltzmann Method） is devel-oped to simulate heat transport,fluid flow,solute diffusion,and dendritic growth,then the solidification process of Al-4.7%Cu alloy is investigated under natural convection.The results show that,the natural convection has a s-ignificant effect on the morphology of dendrites,which makes the growth of dendritic crystals not symmetrical,th-at is to say,the dendritic growth in the upstream under natural flow is promoted,as well as the dendritic growth in the downstream direction is inhibited.The result shows the columnar-to-equiaxed transition in the solidification,the competitive growth and the solute enrichment in the grain boundries.The effect of fluid flow on heat transfer has been studied,which found that the isotherm is strongly influenced by convection,rendering temperature fields tend to be uniform.In addition,the convection can accelerate the solidification process and refine grains.