中文摘要：

对Mg-Zn-Zr合金进行高应变速率多向锻造变形，研究了其组织演变和力学性能。结果表明，高应变速率多向锻造工艺能强烈细化合金的晶粒组织，形成由蜂窝状粗大再结晶组织和岛状细小再结晶组织构成的新颖组织，初始晶界附近和初始晶粒内部的再结晶机制分别是旋转动态再结晶和孪生诱发动态再结晶。由于高应变速率多向锻造工艺具有强烈的晶粒细化能力并能有效避免强烈的基面织构，可大幅提高合金的综合力学性能。累积应变∑△ε=2．64时，ZK21和ZK60抗拉强度、屈服强度和延伸率分别为341．6MPa、270．7MPa、25．1％和330_2MPa、232.3MPa、24．8％。

英文摘要：

High strain rate triaxial-forging （HSRTF） was successfully conducted on three Mg - Zn - Zr alloys by using a pneumatic power hammer. The microstructure evolution and mechanical properties of the forged alloys were investigated. The results show that HSRTF significantly refined the grains due to dynamic recrystallization （DRX）. A novel microstructure was obtained, which was mixed by honeycombe- like coarse DRX grains and island-like ultrafine DRX grains. The two features,of the mixed microstructure were caused by different DRX mechanisms, i.e., rotation DRX at the initial grain boundaries and twin-in- duced DRX in the interior of the initial grains. The mechanical properties were dramatically improved, re- sulting from the severe grain refinement and weakening of the basal texture due to HSRTF.For ZK21 and ZK60 alloys, after HSRTF with an accumulative strain ∑△ε=2.64, excellent tensile properties were achieved with an ultimate tensile strength, yield strength and elongation of 341.6 MPa, 270.7 MPa, 25.1% and 330.2 MPa, 232.3 MPa, 24.8%, respectively.