热处理方式对Mg-Gd-Y-Zr合金组织和力学性能的影响

Effect of heat treatments on microstructure and mechanical properties of Mg-Gd-Y-Zr alloy

采用金相显微镜、扫描电镜、透射电镜、电子背散射衍射及拉伸试验机等研究固溶处理和时效处理对铸态和轧制态Mg-10.6Gd-1.69Y-0.42Zr(质量分数,%)合金显微组织及力学性能的影响。结果表明:经峰时效处理后合金强度均显著提高,但伸长率有所降低;与200℃峰时效态合金相比,220℃峰时效态合金的屈服强度相差不大,但伸长率明显提高。合金在峰时效阶段的主要强化相为柱面β’相,该相能够有效阻碍位错的基面滑移,提高合金强度。轧制后直接时效的合金能够保留轧制产生的位错,而位错能够促进析出相形核,此时,合金具有最高的析出强化效果,屈服强度和抗拉强度分别为380.0 MPa和416.0 MPa。

The effects of solution treatment and aging treatments on microstructure and mechanical properties of as-cast and rolled Mg-10.6Gd-1.69Y-0.42Zr(mass fraction,%) alloy were investigated by optical microscopy,scanning electron microscopy,transmission electron microscopy,electron back-scattered diffraction and materials testing machine.The results show that the strength of the alloy can be improved effectively by peak-aged treatment,but the elongation of the alloy decrease.Compared with the 200 ℃ peak-aged alloy,the yield strength of 220 ℃ peak-aged alloy has little difference,but the elongation increases obviously.Prismatic β' phase is the main strengthening phase of peak-aged alloy,and it can effectively inhibit the basal slip,thus improves the strength of the alloy.The alloy ageing directly after rolling can retain the high density dislocation caused by rolling,and the dislocation can promote the nucleation of precipitated phase.In this case,the alloy has the highest precipitation strengthening effect,whose yield strength and ultimate tensile strength are 380.0 and 416.0 MPa,respectively.