中文摘要：

通过对镁合金铸锭后显微组织的观察，结合SEM能谱分析，研究了Ca、Mn元素对镁合金组织的影响。通过研究，发现Mg-2．0Mn的显微组织是由基体组织（α-Mg）和点状析出的组织（α-Mn）组成；Mg-0．5Ca的显微组织是由（α-Mg）基体组织和非平衡结晶形成的Mg2Ca相组成。Ca、Mn对镁合金的组织均有细化作用，当同时加入Ca、Mn合金元素时，镁合金的显微组织会更加细小，晶粒趋于均匀圆整，同时第二相颗粒减少。其原因是：Ca提高了Mn与镁合金的润湿性，提高了Mn的溶解与扩散能力，温度降低Mn原子从合金中析出，为合金凝固提供了大量的晶核。

英文摘要：

In this paper, through the observation on the microstructures of as-cast Mg alloy and SEM energy spectrum analysis, the effect of Ca and Mn on the microstructure of as-cast Mg alloy was studied. It is found that： Mg -2.0Mn alloy is composed of α-Mg matrix and α-Mn, Mg-0.5Ca alloy is composed of α-Mg matrix and Mg2Ca phase forming from non-equilibrium solidification. Ca and Mn element can refine the microstructure of magnesium alloy. When Ca and Mn are added into the alloy simultaneity, the microstructure of magnesium alloy can be refined further, the grain tended to be more homogenous and spherical and the amount of second-phase particle decreases. The reason is that the wet ability of Mn is improved by Ca element, and Mn element can easily dissolved in the magnesium alloy, when the temperature decreases, the Mn element precipitates continuously from the α-Mg matrix, the precipi- tated Mn particles can take as numerous uncles for the alloy solidification.