二元共晶定向凝固的多相场法数值模拟

Multi-phase field simulation of unidirectional solidification for binary eutectic alloys

借助于多相场模型,利用移动盒算法模拟了小Peclet数下二元共晶模型合金的定向凝固过程。同时研究了共晶生长层片间距调整机制。模拟结果表明:当初始层片间距小于最小过冷层片间距时,层片调整通过两相的竞争生长与层片湮没进行;相反,当初始层片间距大于最小过冷理论时,层尖的形核分叉生长使层片生长趋于稳定;再现了共晶1λ振荡不稳定性生长,通过分析局部动力学得出1λ振荡不稳定性生长原因为溶质再分配与共晶两相的体积调整。

The unidirectional solidification process of a binary eutectic model alloy at low Peclet number was simulated by multi-phase field method together with moving box algorithm. The selection mechanism of lamellar spacing was also studied. The simulation results show that, when the initial lamellar spacing is smaller than that under the minimal undercooling theory, to restabilize the lamellae growth, the annihilation of lamellae occurs; on the contrary, new phase at the top of lamellae nucleates. Moreover, the eutectic period-preserving oscillatory instability （1λ oscillatory） is recurred, which results from the solute redistribution and the volume adjustment of two eutectic phases.