二元合金微观偏析的相场法数值模拟

使用耦合溶质场的相场模拟研究了Ni-Cu二元合金枝晶生长过程中固相溶质扩散系数D_s 对枝晶形貌和微观偏析等的影响.计算结果表明，随着D_s的减少，固液界 面前沿溶质扩散层越薄，枝晶生长越有利，枝晶尖端生长的速度越大，侧向分支越发达；D< sub>s越小，固相中溶质成分的波动越强烈，随着D_s的增大，固相中溶质 成分的波动相应减小；溶质微观偏析程度随D_s的增大而减小. 关键词： 相场方法 微观偏析 固相扩散系数 数值模拟

Numerical simulation of solute segregation patterns for a binary alloy using phase-field approach

The dependence of denderitic patterns and solute segregation on solid diffusivit y D_s is studied using a phase-field model which incorporates concentr ation field for Ni-Cu binary alloy dendritic growth. The computed results indica te that with the decrease of solid diffusivity D_s, the smaller become s the thickness of the solute diffusion layer ahead of the interface, which is a dvantageous to the growth of the sidebranching, and the more developed the side- branches. The smaller the solid diffusivity D_s, the more acutely the solute concentration in solid phase fluctuates. With the increment of solid diff usivity D_s, the fluctuations of solute concentration in solid phase a re reduced accordingly. An increased level of solid diffusivity D_s re duces the severity of microsegregation.