U-6%Nb二元合金凝固过程中显微组织与显微偏析的模拟

提出一个改进的计算固相分数的模型,利用该模型及元胞自动机方法根据相图计算将固/液界面区域内固相分数表示为一个一元二次方程,不需假设界面的位置和形状.对U-6%Nb(质量分数)二元合金的凝固组织和显微偏析的模拟结果表明:初始形核部位Nb浓度最高,随着凝固的进行,该部位Nb浓度不断下降;凝固后期晶界区贫Nb,Nb浓度最低可达3%以下.

Modeling solidification microstructure and microsegregation of U-6%Nb binary alloy during solidification process

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%.