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建立了耦合温度场、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,并用该模型研究了Al-4.7%Cu固溶体合金的凝固过程。模拟结果验证了模型的合理性,再现了合金凝固过程中的枝晶形貌和溶质偏析,并定量研究了自然对流、初始温度对溶质分布和微观组织的影响。研究表明,自然对流对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。初始温度对凝固进程和枝晶形貌影响较大,降低初始温度,枝晶生长加快且产生了二次枝晶,并造成枝晶尖端固液界面处溶质浓度偏高,加重了溶质偏析。
A numerical model of CA-LBM coupled with temperature field, flow field and solute field was established. The solidification process of Al-4.7% Cu solid solution alloy was studied by using this model. The simulation results verify the rationality of the model, reproduce the dendrite morphology and solute segregation during solidification, and quantitatively study the effects of natural convection and initial temperature on solute distribution and microstructure. The results show that natural convection has obvious influence on dendritic morphology, dendritic growth asymmetry, that is, dendrite growth in the direction of flow is promoted, dendrite growth in the downstream direction is inhibited. The initial temperature has a great influence on the solidification process and dendritic morphology. Decreasing the initial temperature, the dendrite grows faster and produces secondary dendrites, resulting in higher solute concentration at the solid-liquid interface at the dendrite tip, which aggravates the solute segregation.