采用光学显微镜（OM）、X射线衍射仪（XRD）、带能谱分析（EDS）的扫描电子显微镜（SEM）等分析手段研究了元素Ca对Mg-8Zn-3.2Al-0.9Si-0.3Mn合金基体及Mg2Si相的细化效果及其细化机制。结果表明：Ca的加入能够使Mg2Si初生相由粗大的汉字状变为细小、弥散分布的颗粒状,并使合金基体组织显著细化。Ca对Mg2Si相的变质是以CaSi2作为Mg2Si相的异质形核核心和Ca作为表面活性元素影响其生长两种机制共同作用的结果。由于显微组织的改善,使得合金的室温和高温力学性能均得到提高。
Effects of Ca on the as-cast microstructure of Mg-8Zn-3.2Al-0.9Si-0.3Mn alloy, especially on the modification and/or refinement of Mg2 Si phase in the alloy, were investigated by optical microscopy（OM）, X-ray diffractometry （XRD） and scanning electron microscopy （SEM） with energy dispersive spectrometry （EDS）, etc. The results show that the morphology of Mg2 Si changed from Chinese script-type to small polygonal type and the matrix microstructure is refined by adding Ca. The modification mechanisms of Mg2 Si are that CaSi2 particles provide the heterogeneous nucleation sites for Mg2 Si phase and Ca influences the growth of Mg2 Si phase as the surface-active element. Owing to the improvement of microstructure, the mechanical properties of the alloys containing Ca as comparing with the base alloy at both ambient and elevated temperatures are increased.
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