镁含量对手机中框用压铸Al-10.5Si-5Zn-xMg铝合金组织和力学性能的影响

Effect of Magnesium Content on Microstructure and Mechanical Properties of Die Cast Al-10.5Si-5Zn-xMg Alloy for Cell Phone Frame

采用光学显微镜(OM)、扫描电镜(SEM)、差热分析仪(DSC)和拉伸性能测试等手段,研究了不同Mg含量铸造Al-10.5Si-5Zn-xMg合金的微观组织和力学性能。结果表明,当Mg含量从0增加到0.8%时,合金中α-Al枝晶的面积分数略有增加,促进了少量块状硅相的析出,且其数量和尺寸逐渐增加;富铁相的形态由细小的紧凑颗粒状α-Fe和针状β-A15FeMnSi转变为粗大的骨骼状Al15(Fe,Mn)3Si2相,并且添加超过0.35%Mg后还出现了与共晶硅颜色接近的π-Al8Mg3 (Fe,Mn)Si6富铁相,但富铁相的面积分数随Mg含量的增加变化不明显,此外Mg含量增加还促进了初生Mg2Si相的析出,其形态由短棒状向粗大的汉字状转变。合金在Mg含量为0.5%时综合力学性能最佳,抗拉强度、屈服强度和伸长率分别为265 MPa、204MPa和4.8%。

The micro structure and mechanical properties of Al-10.5 Si-5 Zn-xMg alloys with different Mg contents were studied by optical microscopy(OM),scanning electron microscopy(SEM),differential scanning calorimeter(DSC) and tensile test.The results show that when Mg content increased from 0 to 0.8%,the area fraction of α-Al dendrite in the alloy increased slightly,which promoted the precipitation of a small amount of massive silicon phase,and the number and size of the dendrite gradually increased.The iron-rich phase changes from tiny,compact,granular α-Fe and acicular β-Al5FeMnSi to a thick,skeletal Al15(Fe,Mn)3Si2 phase.Moreover,π-Al8Mg3(Fe,Mn)Si6 iron-rich phase similar to the color of eutectic silicon appeared after adding more than 0.35% Mg.However,the area fraction of iron-rich phase did not change significantly with the increase of Mg content.In addition,the increase of Mg content also promotes the precipitation of primary Mg2Si phase,which change from the shape of short stick to the shape of thick Chinese characters.The alloy has the best comprehensive mechanical properties when Mg content is 0.5%,and the tensile strength,yield strength and elongation are 265 MPa,204 MPa and 4.8%,respectively.