试验研究了Gd含量分别为0、3.83%、5.81%、9.76%镁钆合金的宏观组织、微观组织和第二相.镁钆合金常规凝固组织为α-Mg固溶体和Mg5Gd第二相组成;随着稀土Gd含量增加,晶粒细化,第二相Mg5Gd的分布状态和数量也发生变化,当Gd含量为3.83%时,第二相多数呈颗粒状或短棒状独立分布在晶界处,随Gd含量增加至9.76%,第二相体积分数增加,呈现孤岛状共晶组织;利用3D-CAFE模型模拟计算Mg-5.81%Gd中心等轴晶区所占面积比例与试验结果相吻合,并且模拟结果显示,随着Gd含量由3.83%增大到9.76%,晶粒细化,柱状晶区减少,中心等轴晶区增加.%The macrostructure, microstructure and the second phase of Mg-Gd alloy with 0, 3.83%, 5.81%and 9.76%Gd content were investigated. The conventional solidification of Mg-Gd alloy structure consists ofα-Mg solid solution and Mg5Gd. The distribution and the number of Mg5Gd of second phase with Gd addition also varied, when the Gd content increased from 3.83%to 9.76%, the volume fraction of the second phase increased, presenting the island eutectic structure. The 3D-CAFE simulation results show that the area ratio of center equiaxed crystal of Mg-5.81%Gd was in agreement with the experimental results. In addition, the increase of Gd content would result in grain refinement, the decrease of columnar crystals proportion and increase of central equiaxed grains.
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