铸态Mg-Sn-Si-Sr合金的显微组织与力学性能

采用X射线衍射仪(XRD)、扫描电镜(SEM)和光学显微镜(OM)分别研究Mg-5Sn-xSi-0.5Sr(x=1,2)和Mg-5Sn-ySi-2Sr(y=1,2)合金的相组成和显微组织,采用力学性能试验机测定合金的拉伸性能。结果表明:Mg-Sn-Si-Sr系合金组织由α-Mg、MgSnSr、Mg2Sn、Mg2Si相所组成。Mg2Si相含量随Si元素的增加而增加,加入Sr元素会促进MgSnSr相的形成,抑制相界上Mg2Sn相的析出。Sn和Sr均能够细化Mg2Si相。当Sr含量由0.5%提高到2%(质量分数)后Mg2Si和Mg2Sn相均能得到显著细化,从而显著提高合金的抗拉强度与屈服强度。

Microstructure and mechanical properties of as-cast Mg-Sn-Si-Sr alloys

The phase constituent and microstructure of as-cast Mg-5Sn-xSi-0.5Sr(x=1,2) and Mg-5Sn-ySi-2Sr(y=1,2) alloys were analyzed by X-ray diffractometry(XRD),scanning electron microscopy(SEM) and optical microscopy(OM),respectively.The mechanical tester was employed to obtain the tensile properties of the alloys.The results show that MgSnSr,Mg2Sn and Mg2Si phases are precipitated on the α-Mg phase boundary or in the phase for as-cast Mg-Sn-Si-Sr series alloys.The volume fractions of Mg2Si phase increase with the Si element increasing.The addition of Sr element can promote the formation of MgSnSr phase and inhibit the precipitation of Mg2Sn phase on the phase boundary.While the Mg2Si phase can be refined through adding Sn and Sr elements.Furthermore,when the Sr content increases from 0.5% to 2%(mass fraction),both the Mg2Si and Mg2Sn phases are refined significantly.Therefore,the tensile and yield strengths of the alloys are obviously enhanced.