预变形对锥台剪切变形镁合金组织与性能的影响

Effect of pre-deformation on microstructure and mechanical properties of magnesium alloy processed by frustum shearing deformation

利用WDW3100电子万能试验机对铸态AZ31镁合金试样进行预压缩量0%和3%处理,并采用新型的锥台强剪切挤压变形方法将AZ31镁合金铸棒挤压成板材。通过金相显微镜、拉伸性能测试及断口扫描分析研究预压缩变形对锥台剪切变形镁合金的微观组织与力学性能的影响。结果表明：3%预变形处理对铸态镁合金植入大量的孪晶组织,为后续动态再结晶提供充足的形核点,且镁合金在变形过程中受到剧烈强剪切变形,使得挤压成形板发生了充分的动态再结晶,晶粒细化至4.5μm。预压缩3%镁合金经锥台剪切变形后,伸长率高达23.6%,屈服强度和抗拉强度高达280.4 MPa和225.3 MPa。与预压缩0%的挤压镁合金相比,断裂伸长率提高幅度高达91%,屈服强度和抗拉强度略有降低。挤压温度对镁合金组织性能有重要的影响,预压缩3%的镁合金经290℃锥台剪切变形后,获得均匀细小的晶粒组织,具有优良的综合力学性能。

By using a WDW3100 electronic universal testing machine,0% and 3% pre-deformation were applied to the cast AZ31 magnesium alloy,which were extruded into plates by the new frustum shearing deformation method. Effect of pre-deformation on the microstructure and mechanical properties of extruded magnesium alloy was studied by using optical microscope,tensile properties test and SEM. The results show that a large amount of twins are implanted in the 3% compressed samples,which can provide enough nucleation sites for subsequent dynamic recrystallization,and severe shearing deformation is also applied to the magnesium alloy during the extrusion process,thus triggering fully dynamic recrystallization. Eventually,the grain size can be even refined to 4. 5 μm. As for the plate via 3% compression and frustum shearing deformation,the fracture elongation can be up to 23. 6%,and the yield strength and tensile strength are 225. 3 MPa and 280. 4 MPa,respectively. Compared with that predeformed by 0% and frustum shearing deformation,the fracture elongation increases by91%,and the yield strength and tensile strength are slightly reduced. In addition,the extrusion temperature plays an important role in governing the microstructure and mechanical property of magnesium alloy. Uniform fine grains and excellent comprehensive performance can be obtained for the extruded plate predeformed by 3% and frustum shearing deformation at 290 ℃.