本文针对以往元胞自动机方法中对固相分数计算模型进行了改进，根据相图计算将固液界面区域内固相分数表示为一个一元二次方程，这种方法不需假设界面的位置和形状，使得模型的物理意义更加明确。利用这种方法模拟了U-6%Nb二元合金的凝固组织和显微偏析，模拟结果表明最初形核部位的Nb溶质浓度最高，随着凝固的不断进行，晶核中心部位Nb 溶质浓度不断下降。当凝固要结束的时候，晶粒边界就会形成贫Nb晶界，Nb溶质浓度最低可达3％以下。
An improved model of calculating solid fraction is presented in this paper that the solid fraction of solid/liquid interface zone can be expressed as an second order equation of one variable based on calculating phase diagram, instead of calculating the solid fraction based on the assumptions of the position and the shape of the solid/liquid interface, which make the physical meanings of the model more clearly. Using the model the solidification microstructure and solute microsegregation of U-6%Nb binary alloy are simulated. The simulated results show that Nb concentration in the initial nucleated position is high. As the solidification proceeds, Nb concentration of the nucleus decreases continuously due to the back diffusion in the solid phase. At the end of solidification, there are poor Nb concentration zones formed at the grains boundary where Nb concentration can be lower than 3%.
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