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采用XRD,SEM等手段研究了铸态Mg-5Sn-4Zn (0～2.5)Si合金的显微结构.结果表明,Mg-5Sn-4Zn合金由枝晶状的α-Mg和Mg2 Sn相组成,Si的加入使合金出现汉字状的Mg2Si相.Zn存在于Mg2 Sn和Mg2 Si相中或者固溶到基体中.随着Si含量增加,晶粒逐渐细化,Mg2Sn相的量也逐渐增加.室温拉伸结果表明,Si的加入恶化了合金的力学性能.但在175℃,载荷为55MPa的压缩蠕变试验结果表明,Si可以提高合金的抗蠕变性能.“,”The microstructure of the as-cast Mg-5Sn-4Zn alloy with 0.5％,1.0％,1.5％ and 2.5％ Si additions was observed by XRD (X-ray diffraction),SEM (scanning electron microscopy).The results reveal that besides of α-Mg and Mg2 Sn phase,Mg2 Si with the Chinese script shape can be observed in the Si containing alloys.Zn exists in the Mg2Sn and Mg2 Si phase or dissolves in α-Mg matrix.Grain size in the alloy can be refined with increasing in Si content,and amounts of Mg2Si are increased.The tensile test at the ambient temperature reveals that the Si addition can result in the deterioration of the tensile properties.The compressive creep behavior of the Mg-Sn-Zn-Si alloy at 175 ℃ with loading of 55 MPa was also investigated.The results reveal that the Si addition is helpful for improving the compressive creep resistance of Mg-Sn-Zn alloy.