二元合金微观偏析的相场法数值模拟

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

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Ds对枝晶形貌和微观偏析等的影响.计算结果表明,随着Ds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;Ds越小,固相中溶质成分的波动越强烈,随着Ds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Ds的增大而减小.

The dependence of denderitic patterns and solute segregation on solid diffusivity Ds is studied using a phase-field model which incorporates concentration field for Ni-Cu binary alloy dendritic growth. The computed results indicate that with the decrease of solid diffusivity Ds, the smaller becomes the thickness of the solute diffusion layer ahead of the interface, which is advantageous to the growth of the sidebranching, and the more developed the side-branches. The smaller the solid diffusivity Ds, the more acutely the solute concentration in solid phase fluctuates. With the increment of solid diffusivity Ds, the fluctuations of solute concentration in solid phase are reduced accordingly. An increased level of solid diffusivity Ds reduces the severity of microsegregation.