부산대학교 도서관

The effect of various amounts of Sr (0%-0.09%,mass fraction, the same below) and homogenization treatment on the as-cast microstructure and mechanical properties of Al-Mg-Si-Cu-Mn alloy was investigated by optical microscopy, scanning electron microscopy, differential thermal analysis, X ray diffraction analysis and hardness test, electrical conductivity test and tensile test. The evolution of the second phase in as-cast microstructure and homogenization annealing process were also studied. The results show that the Al-Mg-Si-Cu-Mn alloy mainly includes AlCuMgSi,Mg2Si,AlSi,Al2Cu,Al(MnFe)Si,AlMnSi and Al(MnCrFe)Si phases. The addition of 0.06%Sr in the alloy can transform the needle-like AlSi phase into spherical AlSi phase, and promote the formation of AlFeSi spherical crystalline phase which reduces the stress concentration and improve the strength and plasticity of the alloy. During homogenization,the bulk-like phases and low melting eutectics are dissolved. The Al(MnCrFe)Si phase turns from the original trigonometric and needle-like phases into fine granular phases which are more favourable for the material processing. The homogenization heat treatment process of 540℃ for 8h is suitable for Al-Mg-Si-Cu-Mn-Sr alloy.