时效处理对Mg-10Gd-3Y-0.5Zr合金组织和性能的影响

Effect of aging treatment on microstructure and properties of Mg-10Gd-3Y-0.5Zr alloy

通过X射线衍射、光学显微镜、扫描电镜、极化曲线、阻抗谱等对铸态、时效态Mg-10Gd-3Y-0.5Zr镁合金的显微组织、力学性能及耐蚀性能进行了研究。结果表明：铸态Mg-10Gd-3Y-0.5Zr合金由α-Mg、树枝状相Mg（24）（Gd,Y）5及颗粒状相Mg5（Gd,Y）组成,合金经515℃×8 h固溶＋225℃×36 h时效处理后,树枝状Mg（24）（Gd,Y）5转变为大量薄片状及细长条状的Mg5（Gd,Y）相。室温力学性能测试结果表明,经时效处理后的合金显微硬度增加27.8%,达到101.97 HV0.1,抗拉强度增加52.5%,达到305 MPa,规定塑性延伸强度增加121.3%,达到239 MPa。极化曲线及阻抗谱表明,时效处理后合金的腐蚀电流密度减小,容抗弧半径增大,电荷传递电阻增大,合金耐腐蚀性能增强。

The microstructure,mechanical properties and corrosion resistance of as-cast and aging state Mg-10Gd-3Y-0.5Zr alloy were investigated by means of XRD,OM,SEM,Tafel curves and impedance spectra.The results show that the microstructure of the as-cast Mg-10Gd-3Y-0.5Zr is composed ofα-Mg matrix,dendritic Mg（24）（Gd,Y）5and dot phase Mg5（Gd,Y）.After solid solution at 515℃for 8 h and aging treatment at 225℃for 36 h,the Mg（24）（Gd,Y）5phase at the grain boundaries changes into large amounts of lamellar and strip Mg5（Gd,Y）phase.The microhardness test and tensile test in the room temperature show that after aging treatment,the microhardness of Mg-10Gd-3Y-0.5Zr reaches 101.97 HV0.1,the ultimate tensile strength increases 305 MPa,the yield strength increases to 239 MPa.The Tafel curves indicates that the corrosion current density of as-cast state alloy is lower than aging state,impedance spectra shows that the capacitive loop radius and charge transfer resistance of aging state alloy are bigger than as-cast state,which means the improved corrosion resistance of as-cast alloy after aging treatment.