二次冷轧对超轻双相镁锂合金组织与性能的影响

Effect of double cold reduction on microstructure and properties of ultralight duplex Mg-Li alloy

采用金相显微镜、扫描电子显微镜、硬度计、室温拉伸等手段,探究了二次冷轧对累积变形率60%、不同退火工艺处理LZ91镁锂合金板显微组织与力学性能的影响。结果表明:经过二次冷轧后,α-Mg与β-Li两相组织都沿轧制方向被压扁,出现了一定程度的取向性。其中250℃×1 h退火经二次冷轧后,细小的"扁球状"α相分布在β相晶粒周围,细小晶粒较多,力学性能也达到最好,最大抗拉强度为285 MPa左右,伸长率为34%,硬度值为73.46 HV0.025;拉伸断口可见大量分布密集的韧窝,为韧性断裂。

Using metallographic microscopy,scanning electron microscopy,hardness tester,and room-temperature tensile test,the effect of secondary cold rolling on the microstructures and mechanical properties of LZ91 magnesium-lithium alloy sheet with 60% cumulative deformation and different annealing processes were investigated.The results show that after double cold reduction,grain refinement occurs in both phases of the two phases,and the orientation of coarser α-Mg and finer β-Li phases has appeared.Among them,after 250 ℃× 1 h annealing and double cold reduction,fine"flat spherical"α phase distributes around the grain of β phase,the grain refinement degree is the best and the mechanical properties are the best.The maximum tensile strength is about 285 MPa,the elongation rate is 34%,and the hardness value is 73.46 HV0.025.Tensile fracture shows a large number of densely distributed dimples,which are ductile fractures.