【摘要】 在A356合金成分基础上添加Zr和Sc,获得Al-7Si-0.3Mg-0.2Zr-xSc铸造合金。使用光学显微镜、场发射扫描电镜、XRD物相分析、维氏硬度测试、拉伸试验等方法,研究了不同Sc浓度下合金组织和力学性能的变化。结果表明,随着Sc含量的增加,生成的Al₃（Sc,Zr）化合物起到晶粒细化作用,共晶区的硅相形貌由松散粗大的针片状改善为细密短棒状结构,α-Al基体晶枝晶尺寸减小,二次枝晶臂间距减小至18.5μm。然而,过量Sc影响了合金的整体综合力学性能,当Sc浓度增加至0.3%时,合金性能下降。以0.2wt.%Zr、0.2wt.%Sc加入量合金的力学性能最佳,其硬度69.4HV、抗拉强度229MPa、伸长率10.5%。更多还原

【Abstract】 In this paper, Al-7Si-0.3Mg-0.2Zr-xSc casting alloy is obtained by adding Zr and Sc to A356 alloy composition. The microstructure and mechanical properties of the alloys at different concentrations of Sc are investigated by optical microscope, field emission scanning electron microscope, XRD phase analysis, vickers hardness test and tensile test. The results show that with the increase of Sc content, the generated Al₃（Sc,Zr） compound played a role in grain refinement, and the silicon phase morphology in eutectic region is improved from loose and coarse needle-like shape to a fine short rod-like structure. The crystallite dendrite size of the α-Al matrix is reduced, and the Secondary Dendrite Arm Spacing is decreased to 18.5 μm. However, the excess Sc affected the overall mechanical properties of the alloy. When Sc concentration increased to 0.3%, the properties of the alloy decreased. The best mechanical properties are obtained by adding 0.2wt.%Zr and 0.2wt.%Sc, with a hardness of 69.4HV, tensile strength of 229MPa and elongation of 10.5%.更多还原