中文摘要：

以Mg-5Sn-1．5Al-1Zn-1Si铸态合金为研究对象，分析了Sb元素对合金组织的影响及其作用机理。结果表明，Sb元素优先与Mg反应生成Mg3Sb2相，适量Sb对合金组织具有较强细化作用，汉字状的Mg2Si得到显著变质；Sb通过Mg2（Si，Sn）中间相的桥梁作用，进一步阻断Mg2Si的枝晶生长，这种阻碍作用打破了Mg2Si共晶相的生长条件，使其汉字状形态得到控制；与其他合金元素相比，Sb的抑制因子较低，加入适量Sb有利于提高合金形核率，增加过冷度，对细化铸态组织具有重要作用。

英文摘要：

Mg-5Sn-1.5Al-1Zn-1Si as-cast alloy was used as the research objects to discuss the effect of antimony on microstructure and action mechanism of the alloy. The results indicated that Mg3 Sb2 phase was preferentially formed by alloying element antimony and magnesium base. Appropriate amont of antimony could refine the microstructure of the as-cast alloy strongly. In this process, modification effect of antimony on Chinese script type Mg2 Si was remarkable. The dendrite growth of Mg2 Si phase was blocked by antimony through the bridging of Mg2 （Si, Sn） interphase, which broke the growth condition of Mg2 Si eutectic phase and controlled its Chinese script morphology. Compared with other alloying elements, inhibitory factors of antimony is low. Appropriate amont of antimony is advantageous to improve the nucleation rate, increase the supercooling degree and refine the as-cast structure as well.