Bi对Mg-3Al-3Nd合金显微组织和力学性能的影响

使用扫描电子显微镜(SEM)和光学显微镜(OM)观察、X-射线衍射(XRD)分析以及力学性能测试等手段研究了Bi含量对Mg-3Al-3Nd合金的显微组织和力学性能的影响。结果表明：添加Bi元素可细化Mg-3Al-3Nd合金的组织。当Bi含量(质量分数)为1%时晶粒最小，晶粒尺寸从1854±58 μm减小到890±64 μm；Mg-3Al-3Nd合金由呈网状分布在晶界的Al₁₁Nd₃相和分布在晶内的颗粒状Al₂Nd组成；随着Bi含量的提高Al₁₁Nd₃相和Al₂Nd相的数量减少，晶内的BiNd相数量增加；Bi能明显改善Mg-3Al-3Nd合金室温和高温力学性能，Bi含量为1%时其室温和高温力学性能最佳。室温抗拉强度和延伸率分别为167±2.3 MPa和(16.1±0.3)%，高温抗拉强度及延伸率分别为136±1.7 MPa和(19.3±0.3)%。

Effect of Bi on Microstructure and Mechanical Properties of Mg-3Al-3Nd Alloy

The effect of Bi on the microstructure and mechanical properties of Mg-3Al-3Nd alloy was investigated by scanning electron microscope (SEM), optical microscope (OM), X-ray diffraction (XRD) and tensile test. The results show that the addition of Bi can refine the microstructure of Mg-3Al-3Nd alloy. When the content (mass fraction) of Bi is 1% the grain size of Mg-3Al-3Nd alloy is the smallest, whilst the grain size reduced from 1854±58 μm for the plain Mg-3Al-3Nd alloy to 890±64 μm for the alloy with 1% Bi addition. The Mg-3Al-3Nd alloy is mainly composed of Al₁₁Nd₃ phase distributed at grain boundaries and granular Al₂Nd distributed within grains. With the increasing Bi content, the volume fraction of Al₁₁Nd₃ phase and Al₂Nd phase decrease, and the volume fraction of BiNd phase distributed within grains increases. The mechanical properties of Mg-3Al-3Nd alloy at room temperature and high temperature are significantly improved with addition of Bi. The ultimate tensile strength and elongation at break of Mg-3Al-3Nd alloy with 1% Bi addition at room temperature and high temperature is 167±2.3 MPa and 16.1±0.3%, 136±1.7 MPa and 19.3±0.3%, respectively.