(1. 中南大学 材料科学与工程学院，长沙 410083；
2. 湖南工学院 机械工程系，衡阳 421008)
摘 要: 对初始晶粒度为66 μm的轧制板材在不同温度和不同变形速率下进行超塑性拉伸实验，研究Mg-Gd-Y-Zr合金粗晶热轧板材的超塑性行为与微结构特征。在温度为435 ℃、应变速率为5×10−4 s−1的变形条件下获得的最大伸长率为380%，应变速率敏感系数为0.56。合金的表观变形激活能高于镁的晶界扩散激活能或晶格扩散激活能；合金的超塑性变形机制为晶格扩散控制的位错协调晶界滑动机制。微结构分析结果表明：第二相钉轧晶界，较软的不规则块状的β相承受了部分塑性变形。
关键字: Mg-Gd-Y-Zr合金；热轧；第二相；超塑性变形行为；微结构
（1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Department of Mechanical Engineering, Hunan Institute of Technology, Hengyang 421008, China）
Abstract:The superplastic behavior and microstructural characteristics of coarse-grained Mg-Gd-Y-Zr rolled sheet with initial grain size of 66 µm were investigated systematically, the tensile tests at various temperatures and strain rates were conducted. The results show that the sheet exhibits a maximum elongation of 380% and a sensitivity coefficient of strain rate of 0.56 at 435 ℃ and 5×10−4 s−1. The apparent activation energy of this alloy is larger than the diffusion activation energy of grain bound or lattice diffusion energy of Mg. The superplastic behavior is attributed to grain boundary sliding accommodated by dislocation motion assisted by lattice diffusion. It is suggested from microstructural analysis results that the second phases exhibit significant effect of pinning grain boundaries, and that β phase deforms and the strain partly transfers from the matrix to the β phase.
Key words: Mg-Gd-Y-Zr alloy; hot rolling; second phase; superplastic behavior; microstructure
