Mg-Gd-Y-Nd-Zr合金铸锭的均匀化

采用光学金相、差热分析、扫描电镜、能谱分析和拉伸试验等方法,对比研究Mg-Gd-Y-Nd-Zr合金铸锭非平衡凝固组织熔点(539 ℃)以下(520 ℃)和先于520 ℃保温再在非平衡凝固组织熔点以上(560 ℃)保温这2种不同均匀化制度对合金组织和力学性能的影响.结果表明:Mg-Gd-Y-Nd-Zr合金采用520 ℃保温均匀化后,尽管伪共晶基本消除,但残留较多富稀土粒子,进一步采用560 ℃保温均匀化后,不仅非平衡组织能在较短的时间内消除,而且富稀土粒子相明显减少,伸长率提高50%以上;减少熔炼时形成游离稀土粒子和在高于非平衡凝固组织熔点以上保温均匀化是提高该合金伸长率的有效途径.

Homogeneity of Mg-Gd-Y-Nd-Zr alloy as-cast

The influence of two different homogenization heat treatment, one at temperature below the melting point of pseudo-eutectic (MPPE, 539 ℃) and another include treating below MMPE followed by treating above MPPE, on the microstructures and mechanical properties of Mg-Gd-Y-Nd-Zr alloy was investigated with OM, DTA, SEM, EDS and tensile test. The results show that, almost all the pseudo-eutectics disappear after the homogenization heat-treatment at 520 ℃, but some rare-earth-rich particles remain. While after the further homogenization heat-treatment at 560 ℃, the amount of rare-earth particles decreases dramatically. Therefore, the elongation rate of the two-stage homogenized samples increases by 50% with the decrease of the rare-earth-rich particles. This reveals that decreasing the dissociatived rare-earth particles and being homogeneity-heat-treated at temperature more than the MPPE are effective ways to improve the elongation of the present Mg-Gd-Y-Nd alloy.