建立了基于元胞自动机(CA)和热力学相平衡计算引擎(PanEngine)的二维耦合模型, 并应用于铝 基四元合金枝晶组织和微观偏析的数值模拟. 在该耦合模型中, 采用CA方法模拟枝晶组织的演变. 以固/液界面的平衡液相线温度和实际温度的差值作为枝晶生长的驱动力, 同时考虑了固/液界面曲率的Gibbs-Thomson效应. 通过求解溶质传输方程获得固/液界面处三种溶质的液相成分, 耦合PanEngine获得固/液界面处的平衡液相线温度及三种溶质的平衡固相成分. 为提高计算效率, 采用预制数据表格的优化策略将CA与PanEngine进行耦合. 将Al-4.5Cu-0.5Mg-1Si(质量分数, %)四元合金凝固时的固相分数随温度的变化以及固相分数和固相成分分布关系的模拟结果与Scheil模型和平衡凝固模型的预测结果进行了对比, 结果表明, 该模型不仅可应用于模拟多元合金中的枝晶生长形貌, 而且能对铝基四元合金系凝固的微观偏 析进行定量预测.
A two-dimensional (2-D) coupled cellular automaton (CA)-PanEngine model is developed for the simulation of dendritic growth and microsegregation formation in solidification of quaternary alloy system. In the model, the CA approach is employed to describe dendritic growth. The dynamics of dendritic growth is calculated according to the difference between the local equilibrium liquidus temperature and local actual temperature, incorporating with the Gibbs–Thomson effect. Based on the local liquid compositions of three solutes, which are determined by solving the solutal transport equation in the domain, the local equilibrium liquidus temperature and equilibrium solid concentrations of three solutes at the solid/liquid (SL) interface are evaluated with the aid of a thermodynamic phase equilibrium calculation package PanEngine. To reduce computation time, a data tabulation coupling strategy between CA and PanEngine is adopted. The model is validated through the comparisons of simulated results with the predictions of the Scheil model and the equilibrium model for the evolution of solid fraction with the decrease of temperature and for the solid composition profiles as a function of solid fraction in an Al-4.5wt%Cu-0.5wt%Mg-1wt%Si alloy. It is demonstrated that the present model can be used to simulate the evolution of dendritic growth morphology and to quantitatively predict the microsegregation patterns in solidification of quaternary Al-rich alloys.
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