反复扭转变形对铸态AZ61镁合金组织及疲劳性能的影响

Effect of Cyclic Torsion Deformation on Microstructure and Fatigue Properties of As-cast AZ61 Mg Alloy

对AZ61镁合金进行反复的扭转变形加工,获得了具有孪晶和细晶梯度层合金表层。采用弯曲试验和低周疲劳试验研究了梯度组织对AZ61镁合金在恒应力疲劳加载条件下的变形行为和疲劳寿命的影响。结果表明:扭转试样从中心层到表层,孪晶层逐渐增多和细晶层晶粒尺寸逐渐减小。梯度组织使得弯曲强度提高185 MPa并且保持延性几乎不降低;同时梯度组织可改变AZ61镁合金的循环应力-应变行为,在低的总应力下,梯度组织可提高AZ61镁合金的疲劳寿命。

AZ61 Mg alloy was deformed by cyclic torsion, so the gradient layer with twins and fine grains could be obtained on the surface of the sample. The effects of gradient microstructure on the deformation behavior and fatigue life of AZ61 Mg alloy under constant stress fatigue loading were studied by bend test and low cycle fatigue test. The results show that the amount of twins gradually increase while the grain size gradually decreases from the center layer to the surface layer of the sample after torsion. The gradient structure makes the bending strength increase by 185 MPa without losing any ductility. Besides, the gradient structure can change the cyclic stress-strain behavior of AZ61 Mg alloy. The fatigue life of AZ61 Mg alloy improves under low total stress.