Ce元素对Mg-Gd-Y-Nd-Zr合金组织与热变形行为的影响

Effects of Ce addition on microstructures and hot deformation behaviors of Mg-Gd-Y-Nd-Zr alloy

采用Gleeble1500D热模拟机,对Mg-5.5Gd-4.5Y-1Nd-xCe-1Zr(x=0和0.2%,质量分数)合金进行热压缩变形实验(实验温度为375～525℃,应变速率为0.01、0.1和1s1,最大变形量为50%),并对合金的塑性变形行为以及变形后的组织进行研究。研究结果表明:合金在变形温度为375℃、应变速率为0.01s1条件下开始发生动态再结晶;随着变形温度的升高或应变速率的降低,再结晶体积分数逐渐增加,再结晶晶粒粒径逐渐变大;添加Ce元素可提高再结晶体积分数,减小再结晶晶粒粒径;固溶过程中出现的"椭球状"Mg12Ce粒子对再结晶有粒子激发形核(PSN)作用;这2种合金在375～525℃下的变形表观激活能分别为191和212kJ/mol。

Simulation experiments of constant-strain-rate hot-compression for Mg-5.5Gd-4.5Y-1Nd-xCe-lZr （x=0 and 0.2%, mass fraction） alloys were carried out with the conditions of temperatures of 375-525℃, strain rates of 0.01, 0.1, 1 s-1 and a maximum deformation reduction of 50% by Gleeble-1500D thermal simulators. Then, its plastic deformation behavior and microstructures were investigated. The results indicate that the dynamic recrystallization starts to occur under the condition of 375 ℃ and strain rate of 0.01 s^-1; and the volume fraction of recrystallization and recrystallized grain size increases gradually as the temperature increases or strain rate decreases. Addition of Ce increases the recrystallization volume fraction, and decreases the recrystallization grain size; the ellipsoidal Mgl2Ce particles occurring during solution can accelerate recrystallization by the mechanism of particle stimulated nucleation（PSN）. The apparent activation energy of two alloys at 375-525℃ are 191 and 212 kJ/mol, respectively.