初始晶粒尺寸对大应变轧制AZ31镁合金板材显微组织和力学性能的影响

Effect of Initial Grain Sizes on Microstructure and Mechanical Properties of AZ31 Magnesium Alloy Sheets Fabricated by Large Strain Rolling

对自行熔炼制备的AZ31镁合金铸锭进行挤压并在350℃进行不同时间的退火处理,以得到具有不同初始晶粒尺寸的板材,然后对其在40%和80%的压下量下进行轧制,研究了初始晶粒尺寸对轧后板材显微组织和力学性能的影响。结果表明:经大应变轧制(压下量80%)后,合金组织得到明显细化,孪生诱发动态再结晶和旋转动态再结晶是大应变轧制过程中主要的再结晶机制;随着初始晶粒尺寸的增大,晶粒转动作用受到抑制,孪生作用增强,孪生诱发动态再结晶成为再结晶的主导机制,从而获得了均匀的再结晶组织和优异的力学性能;当压下量为80%时,初始大尺寸晶粒板材的平均晶粒尺寸为5μm,其抗拉强度、屈服强度和伸长率分别为311.3 MPa,206.8MPa和28.3%。

AZ31 magnesium alloy ingot was self-prepared,extruded and annealed at 350℃ for different times in order to obtain the alloy sheet containing initial grains with different sizes,and then the sheet was rolled with reductions of 40% and 80%.The effects of initial grain sizes on microstructure and mechanical properties of the rolled sheet were investigated.The results show that the microstructure was significantly refined after large strain rolling with reduction of 80%,the main recrystallization mechanisms were twining induced dynamic recrystallization and rotation dynamic recrystallization.The role of grain rotation was restrained while the role of twinning was enhanced with the increase of initial grain sizes,therefore the role of twining induced dynamic recrystallization dominated,consequently,the homogeneous recrystallization microstructure and good mechanical properties were obtained.When the reduction was 80%,the tensile strength,yield strength and elongation of the magnesium sheet with the largest initial grain size of 5μm were 311.3MPa,206.8MPa and 28.3%,respectively.