中文摘要：

采用光学电镜（OM）、扫描电镜（SEM）、物相分析（XRD）以及透射电镜（TEM）等手段，研究Mg-xGd-Zr（x=1%、2%、3%，摩尔分数）合金均匀化处理前后组织演变及方块相的成分结构。结果表明：方块相为Gd2O3，均匀化处理前后其结构皆为FCC，晶格常数a=0.53 nm。铸态合金中Gd2O3数量较少且基本位于共晶组织附近，且随着均匀化时间的延长，共晶组织回溶，Gd 2 O 3数量明显增多，且随着合金中Gd含量的增高而显著增加。在合金熔炼和凝固过程中生成了少量的Gd2O3，但大部分是在均匀化处理过程中晶界附近富Gd区氧化形成的。

英文摘要：

The microstructure evolution of Mg-xGd-Zr（x=1%, 2%, 3%, mole fraction） alloys as well as the micro- structure of the cubic-shaped phase before and after homogenization were investigated by optical microscopy （OM）, scanning electron microscopy （SEM）, X-ray diffractometry （XRD） and transmitted electron microscopy （TEM）. The results show that the cubic-shaped phase is Gd2O3and the structure is stable as FCC with the lattice constanta=0.53 nm before and after homogenization. Gd2O3are enwrapped in the eutectic structure in the as-cast alloys, and the number increases obviously with increasing homogenization time. Furthermore, the number is proportional to the Gd content in the alloys. Gd2O3 nucleate and grow in the solidification process, whereas, mostly are formed in Gd-rich area near grain boundaries during the homogenization.