基于KKS模型二元合金等温凝固过程的相场法模拟

基于KKS模型,采用相场和溶质场两场耦合的方法,对Al-2-mole-Cu合金凝固过程枝晶生长进行了数值模拟.在模拟过程中,采用不同的各项异性系数和初始晶核固液界面溶质浓度梯度.模拟结果表明,在没有扰动的情况下,随着各项异性系数的增大,枝晶出现二次枝晶,且越发达,并伴随着“颈缩”现象,当各项异性值达到足够大时,二次枝晶就会由于凝固潜热的释放而出现熔化“脱落”现象,脱落的二次枝晶将会成为非均质形核的初始晶核.模拟结果还表明,时间步长的增大不是致使模拟枝晶出现分叉的唯一原因,小的各项异性系数也会使枝晶出现分叉现象.

Phase-field simulation of isothermal solidification of binary alloy based on KKS model

The phase-field model coupled with the concentration field is used to simulate microstructural dendrite growth of the alloy Al-2-mole-Cu.In simulation,different anisotropy coefficients and concentration grads were used,the calculation results indicate that,with the increasing of anisotropy coefficient,the side-branches are of upgrowth;when the anisotropy coefficient is big enough,the side-branch will broken off,which will be as the new growth nucleus.The result also indicates that the big time step is not the only reason for branch off of dendrite growth,small anisotropy coefficient can also impel the branch off too.