等温模锻对AZ91D镁合金组织和性能的影响

Effects of isothermal forging on microstructures and mechanical properties of AZ91D magnesium alloy

采用金相分析、拉伸试验、SEM分析等方法测试和分析了AZ91D镁合金在铸态、锻压态及锻后+人工时效处理态下的金相显微组织和力学性能。研究表明:锻前均匀化退火能使沿晶界分布的网状β-Mg17Al12相全部溶入基体α-Mg中;等温模锻成形过程中,合金发生了明显的动态再结晶,形成细小的再结晶等轴晶粒组织,合金力学性能相对铸态有大幅提升;锻后人工时效,合金中重新弥散析出β-Mg17Al12相,合金强度提升,而塑性有所下降。3种状态下合金断口形貌均呈现出混合断裂的特征。

The microstructure analysis,tensile test and SEM analysis were used to investigate the microstructure and properties variation of AZ91D alloy in under cast,forged and artificial aging states.The results show that the net β-Mg17Al12 distributed along the grain boundary is almost dissolved during homogenization before forging.The mechanical properties are remarkably improved after isothermal forging with the refinement of the grain size due to the DRX occurs.After artificial aging treatment,with the dispersed precipitation of β-Mg17Al12 phase,the ultimate tensile strength is improved but with a slight decrease of elongation.The fracture morphology of the alloy in different states is all characterized by mixed fracture.