根据hcp晶体学结构和优先生长方向, 建立了铸造镁合金晶体生长的物理模型, 提出了一种新的随机性模拟方法——虚拟生长中心计算模型. 模型考虑了枝晶生长动力学、各向异性和二次枝晶臂粗化, 采用枝晶形状函数揭示了一 次枝晶和二次枝晶的生长演化过程. 引入坐标变换技术可更快速准确计算任意晶向枝晶的生长捕获. 耦合了微观溶质场计算, 得到了更准确的枝晶生长形貌和溶质分布情况. 对Mg-Al合金定向凝固和等轴晶生长的模拟验证了本模型的正确性.
Magnesium alloy is getting more and more worldwide application. Therefore, microstructure simulation of Mg alloy during solidification process not only has important academic value, but also can meet the active demand for development of industry. Based on the crystallographic structure and preferential growth direction of Mg alloy, physical model of grain growth for compact hexagonal structure was founded and a new stochastic simulation method named virtual core growth calculation model was proposed in this paper. Considering dendrite growth kinetics, anisotropy of grain growth and secondary dendrite arm coarsening, the present model adopted dendrite shape functions to reveal the evolution of primary and secondary dendrite arms. A coordinate transformation technique was introduced to calculate the cell capture of growing dendrites with arbitrary orientations rapidly and accurately. Coupled with the calculation of microscopic solute concentration, the simulation can get more accurate growth morphology of dendrites and solute distribution. Finally, applications to the Mg-Al based alloys are presented describing directional as well as equiaxed dendritic growth, which indicated the high theoretic and practical value of proposed models.
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