AZ31镁合金高应变速率轧制边裂及力学性能各向异性

Edge crack and anisotropy of mechanical properties of AZ31 magnesium alloy under high strain rate rolling

在300~400℃对铸态AZ31镁合金进行平均应变速率为10~29 s-1的高应变速率轧制,研究轧制后镁板边裂、组织及力学性能的各向异性。结果表明:随着平均应变速率的增加,轧制边裂得到改善,350℃和400℃下边裂长度变化相比300℃时更加平缓;晶粒尺寸在温升和应变速率综合作用下并不随平均应变速率的增加而减小,反而出现波动;在相对较低的应变速率下,由于组织中长条形晶粒的存在,导致板材的各向异性明显;随着平均应变速率的增加,长条形晶粒减少,再结晶完全,组织趋于均匀,轧板的各向异性得到改善;轧板拉伸断口中可观察到撕裂棱和韧窝,以韧性断裂方式为主。

High strain rate rolling was carried out on as-casting AZ31 magnesium alloys over the temperature ranges 300 to 400 ℃ with average strain rates of 10-29 s-1. The edge cracks,microstructures and anisotropy of mechanical properties were investigated. The results show that with increasing the average strain rate,edge crack is improved. The change of edge crack length at 300 ℃ is more obvious than that at 350 ℃ and 400 ℃.Affected by the temperature rise and average strain rate,the grain size does not decrease,but fluctuates with average strain rate increasing. At a relatively low strain rate,the anisotropy of the sheet is obvious due to the existence of enlongated grains.With the increase of the average strain rate,the amount of enlongated grains decreases and the microstructures are gradually uniform,which can be attributed to the complete recrystallization. Finally,the anisotropy of the sheet is improved. The ductile fracture is the main fracture mechanism for the rolled sheet.