(1. 南昌航空大學(xué) 輕合金加工科學(xué)與技術(shù)國(guó)防重點(diǎn)學(xué)科實(shí)驗(yàn)室，南昌 330063；
2. 俄亥俄州立大學(xué) 工程學(xué)院，哥倫布，俄亥俄州 43210，美國(guó))
摘 要: 以AZ91D合金為例，模擬研究鎂合金凝固時(shí)的溶質(zhì)分布情況，著重定量分析過冷度ΔT對(duì)枝晶尖端前沿最高溶質(zhì)濃度、枝晶干軸對(duì)稱中心溶質(zhì)濃度、枝晶尖端溶質(zhì)擴(kuò)散層厚度以及溶質(zhì)偏析比的影響。模擬結(jié)果表明：貧Al區(qū)主要集中于一次枝晶干和二次枝晶臂的軸對(duì)稱中心，過冷度ΔT越大，枝晶尖端前沿溶質(zhì)濃度 越高，枝晶干中心溶質(zhì)濃度 越高，枝晶尖端前沿溶質(zhì)擴(kuò)散層厚度δ越小，偏析比SR越大，微觀偏析越嚴(yán)重，其具體關(guān)系分別為 ＞ ＞ ＞ 、 ＞ ＞ ＞ 、δ1＜δ2＜δ3＜δ4和SR1＞SR2＞SR3＞SR4。
關(guān)鍵字: 鎂合金；相場(chǎng)法；微觀偏析；計(jì)算機(jī)模擬；密排六方結(jié)構(gòu)
（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
