微量Sr及均匀化工艺对Al-Mg-Si-Cu-Mn变形铝合金铸态组织与性能的影响

采用光学显微镜、扫描电镜、差热分析、X射线衍射分析及硬度测试、电导率测试、拉伸测试等方法,研究了0%～0.09%Sr(质量分数,下同)含量和均匀化工艺对Al-Mg-Si-Cu-Mn变形铝合金铸态组织及性能的影响,并对合金铸态组织及均匀化退火过程中第二相的演变进行了分析。结果表明:Al-Mg-Si-Cu-Mn铸态合金主要包括AlCuMgSi,Mg_2Si,AlSi,Al_2Cu,Al(MnFe)Si,AlMnSi和Al(MnCrFe)Si等结晶相,在合金中加入0.06%Sr可使铸锭中针状Si相转变为球状相,并促进球状AlFeSi型结晶相的形成,减小了应力集中,提高了合金铸态的强度及塑性;在均匀化退火过程中,随保温时间的延长,块状相和低熔点共晶组织溶解,Al(MnCrFe)Si相由原来的三角块状和针状相转变成细小的颗粒状相,Al-Mg-Si-Cu-Mn-Sr合金的最佳均匀化热处理工艺为540℃×8h。

Effect of minor strontium and homogenization process on as-cast microstructure and mechanical properties of Al-Mg-Si-Cu-Mn wrought aluminum alloy

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 l^hermal analysis,X ray diffraction analysis and hardness test,electrical conductivity test and tensile test.The evo lution of the second phase in as-cast microstructure and homogenization annealing process were also studied.The results show that the Al-Mg-Si-Cu-Mnalloy mainly includes AlCuMgSi,Mg2 Si,AlSi,AlCu,Al(MnFe)Si,AlMnSi and A1(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 forAl-Mg-Si-Cu-Mn-Sr alloy.