Mg-9Gd-4Y-1Zn-0.5Zr合金的组织和性能

Microstructure and properties of Mg-9Gd-4Y-1Zn-0.5Zr alloy

采用X射线衍射仪、光学显微镜、扫描电镜、能谱分析仪以及拉伸试验机,研究了不同热处理对Mg-9Gd-4Y-1Zn-0.5Zr合金组织和性能的影响。结果表明:不论是铸态、固溶态,还是时效态,合金组织都主要由α-Mg基体以及稀土化合物Mg5(Gd,Y,Zn)、Mg24(Y,Gd,Zn)5和Mg12Zn(Gd,Y)组成;但铸态下合金中第二相主要为Mg5(Gd,Y,Zn),在晶内呈平行的流线状排列,晶粒粗大。通过固溶时效处理,Mg12Zn(Gd,Y)相在晶界处析出并向晶内生长,成为合金的主要强化相,其强化方式主要为固溶强化和时效强化。室温下,铸态合金抗拉强度为138 MPa,伸长率为2.16%,时效态合金抗拉强度为223 MPa,伸长率为3.94%,合金力学性能得到明显提升。

Microstructure and mechanical properties of Mg-9Gd-4Y-1Zn-0.5Zr alloy after different heat treatments were studied by means of XRD,OM,SEM,EDS analysis and tensile testing machine.The results show that in the state of casting,solid solution and aging,the microstructure of the alloy is mainly composed of α-Mg matrix and Mg5（Gd,Y,Zn）,Mg（24）（Y,Gd,Zn）5,Mg（12）Zn（Gd,Y） rare earth compounds.The second phase of the as-cast alloy is mainly Mg5（Gd,Y,Zn） phase,which is parallel streamline-like with coarsegrain.After solution and aging treatment,Mg12Zn（Gd,Y） phase precipitates at grain boundaries and grows into the crystal,which is the main strengthening phase of the alloy,and the strengthening methods are mainly solid solution strengthening and aging strengthening.At room temperature,the tensile strength of the as-cast alloy is 138 MPa with the elongation of 2.16%,and the tensile strength of the aged alloy is 223 MPa,exhibiting the elongation of 3.94%.The mechanical properties of the alloy are improved obviously.