(1. 南昌航空大学 轻合金加工科学与技术国防重点学科实验室，南昌 330063；
2. 俄亥俄州立大学 工程学院，哥伦布，俄亥俄州 43210，美国)
摘 要: 以AZ91D合金为例，模拟研究镁合金凝固时的溶质分布情况，着重定量分析过冷度ΔT对枝晶尖端前沿最高溶质浓度、枝晶干轴对称中心溶质浓度、枝晶尖端溶质扩散层厚度以及溶质偏析比的影响。模拟结果表明：贫Al区主要集中于一次枝晶干和二次枝晶臂的轴对称中心，过冷度ΔT越大，枝晶尖端前沿溶质浓度 越高，枝晶干中心溶质浓度 越高，枝晶尖端前沿溶质扩散层厚度δ越小，偏析比SR越大，微观偏析越严重，其具体关系分别为 ＞ ＞ ＞ 、 ＞ ＞ ＞ 、δ1＜δ2＜δ3＜δ4和SR1＞SR2＞SR3＞SR4。
关键字: 镁合金；相场法；微观偏析；计算机模拟；密排六方结构
（1. National Defence Key Discipline Laboratory of Light Alloy Processing Science and Technology Institute,
Nanchang Hangkong University, Nanchang 330063, China;
2. School of Engineering, The Ohio State University, Columbus, OH 43210, USA）
Abstract:Based on the KKS model which couples the phase field, concentration field and temperature field, the phase-field model for the magnesium alloys with hcp structure was developed, taking AZ91D magnesium alloy for example, the solute distribution during the metal solidification was simulated, the effects of supercooling (ΔT) on the highest solute concentration in front of the dendrite tip, the solute concentration value in the axis center of dendrite arm, the thickness of solute diffusion layer of aluminum in front of dendrite tip and solute segregation ratio were studied emphatically and quantitatively. The simulation results show that the zone of poor Al distributes in the axisymmetric center of primary dendrite arms secondary dendrite arms, the larger the supercooling ΔT is, the higher the concentration maximum value in front of the dendrite tip is, the higher the concentration value in the axis center of dendrite arm is, the smaller the boundary thickness δ of concentration in front of the dendrite tip is, the bigger the segregation ratio SR is and the severer the microsegregation is. The relationships are ＞ ＞ ＞ , ＞ ＞ ＞ , δ1＜ δ2＜δ3＜δ4 and SR1＞SR2＞SR3＞SR4, respectively.
Key words: magnesium alloy; phase-field method; microsegregation; computer simulation; hexagonal close-packed structure
