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基于KKS模型,耦合温度场、浓度场、流场和取向场,建立适合hcp晶系镁合金的相场模型,研究强迫对流下镁合金单晶粒和多晶粒生长过程。结果表明:在v=0.02 m/s的水平强迫对流作用下,晶粒上游侧3个方向的一次枝晶臂生长速度明显快于下游侧3个方向的一次枝晶臂,同一时刻上游方向一次枝晶臂最长,上游侧与水平方向成60o夹角的两枝晶臂次之,下游侧与水平方向成60o夹角的两枝晶臂较短,下游方向枝晶臂最短。多晶粒生长时,晶粒间相互影响,不同晶粒的枝晶臂相互碰撞并彼此抑制,最终形成不对称枝晶形貌。将模拟结果与实验结果进行对比表明,镁合金连续形核下多晶粒枝晶形态的模拟结果与实验结果十分相似,从而验证了本文中相场模型的正确性。
Based on the KKS model, the coupled temperature field, the concentration field, the flow field and the orientation field, a phase field model suitable for the hcp crystal magnesium alloy was established to study the growth of single-crystal and multi-crystal grains of Mg alloy under forced convection. The results show that the primary dendrite arm in three directions on the upstream side of the grain grows faster than the primary dendrite arm in the three directions at the downstream side under the forced convection of v = 0.02 m / s, and the upstream direction at the same time The dendrite arm is the longest, followed by the two dendrite arms with an angle of 60o between the upstream side and the horizontal direction. The two dendrite arms with a 60o angle between the downstream side and the horizontal direction are short, and the dendrite arm in the downstream direction is the shortest. During the growth of multi-grains, the grains interact with each other and the dendrite arms of different grains collide with each other and restrain each other, resulting in an asymmetric dendrite morphology. Comparing the simulation results with the experimental results, it is shown that the simulation results of the multi-grain dendritic morphology under the continuous nucleation of magnesium alloy are very similar to the experimental results, and the correctness of the phase field model in this paper is verified.