第二相对Mg-Ca-Sn镁合金铸态组织和力学性能的影响

Effect of Second Phases on Microstructure and Mechanical Properties of As-Cast Mg-Ca-Sn Magnesium Alloy

摘要:

研究了含有不同第二相的金属型铸造Mg-Ca-Sn镁合金的显微组织和力学性能。结果表明：在合金中Ca和Sn单独存在可以在一定程度抑制铸态基体晶粒长大，Mg2Ca在晶界或枝晶界处连续分布，Mg2Sn呈颗粒状在晶界和晶内分布。Ca和Sn同时存在时，有CaMgSn在基体上呈半连续的点状或针状，在凝固过程中可作为α-Mg的异质形核核心，与单独添加相比，镁基体的铸态晶粒尺寸显著细化。运用边-边匹配模型分析了CaMgSn化合物与α-Mg之间的异质形核晶体学关系。晶粒细化后的Mg-Ca-Sn镁合金的显微硬度得到明显提高。

Abstract:

The effects of second phases on microstructure and mechanical properties of as-cast Mg-Ca-Sn permanent moulding magnesium alloy were investigated. The results indicate that sole addition of Ca and Sn refined grain size of as-cast magnesium alloy in a certain degree. Mg2Ca phase precipitated at grain boundaries continuously and granular Mg2Sn phase existed at grain boundaries and inside the grains. Point and needle-like CaMgSn phase can be formed after Ca and Sn combined addition. Because CaMgSn particles acted as heterogeneous nucleus of α-Mg during solidification, the grain of α-Mg was significantly refiner than sole addition one. The edge-to-edge matching model was used to analyze the crystallography mismatch relationship between CaMgSn and α-Mg. Microhardness of Mg-Ca-Sn magnesium alloy was improved remarkably with finer grain size.