Si和Ca对铸态Mg-5Sn-0.5Sr合金组织和性能的影响

为了提高镁合金的耐热性能,在Mg-5Sn-0.5Sr合金中加入Si和Ca等合金化元素,设计了Mg-5Sn-0.5Sr-xSi(x=1,2)和Mg-5Sn-0.5Sr-xSi-0.5Ca(x=1,2)合金.采用x-射线衍射仪(XRD)、光学显微镜(OM)与扫描电镜(SEM)研究了合金的相组成及显微组织,并利用力学性能试验机测定了合金的拉伸性能.结果表明,Mg-5Sn-0.5Sr-xSi(x=1,2)合金组织由沿α-Mg晶界析出的共晶Mg₂Sn、Mg₂Si相与α-Mg晶内初生MgSnSr相组成,且Mg₂Si相的质量分数随Si元素的增加而增加.对于Mg-5Sn-0.5Sr-xSi-0.5Ca(x=1,2)合金而言,加入Ca元素能够显著促进初生(Ca,Sr)MgSn相的形成,而抑制晶界上Mg₂Sn相的析出.

Effect of Si and Ca on microstructures and mechanical properties of as-cast Mg-5Sn-0.5Sr alloy

In order to improve the heat resistance of magnesium alloys, such alloying elements as Si and Ca were added into the Mg-5Sn-0.5Sr alloy, and the Mg-5Sn-0.5Sr-xSi(x=1, 2)and Mg-5Sn-0.5Sr-xSi-0.5Ca(x=1, 2)alloys were designed. The phase constituent and microstructures of the alloys were studied with x-ray diffractometer(XRD), optical microscope(OM)and scanning electron microscope(SEM), respectively. In addition, the tensile properties of the alloys were tested with the mechanical property tester. The results show that the microstructures of Mg-5Sn-0.5Sr-xSi(x=1, 2)alloys were composed of Mg₂Sn and Mg₂Si eutectic phases precipitated along the α-Mg grain boundaries as well as primary MgSnSr phase formed in the α-Mg grains, and the quantity of Mg₂Si phase increases with increasing the Si content. For the Mg-5Sn-0.5Sr-xSi-0.5Ca(x=1, 2)alloys, the addition of Ca element can significantly promote the formation of primary(Ca, Sr)MgSn phases, while inhibit the precipitation of Mg₂Sn phase along the grain boundaries.