Chen Hongbing, Shen Zhikang, Song Bo, She Jia
College of Engineering and Technology, Southwest University, Chongqing 400715, China.
School of Materials and Energy, Southwest University, Chongqing 400715, China.
Materials (Basel). 2023 Jul 29;16(15):5343. doi: 10.3390/ma16155343.
In this study, the influence of pre-tension on free-end torsion behavior and compression mechanical properties and micro-hardness of an extruded AZ31 Mg alloy was investigated using electron backscatter diffraction (EBSD), compression testing and micro-hardness testing. The result indicates that pre-tension can cause significant dislocation strengthening, which can increase the torsion yield strength and make the shear stress-shear strain curve of the pre-tension sample almost parallel to that of the as-extruded sample during plastic deformation stage. Texture in edge position on the cross-section of both the pre-tension and as-extruded samples can be rotated towards the extrusion direction by about ~30° by free-end torsion. The Swift effect is mainly responsible for the occurrence of massive extension twins in the central region. In contrast, normal stress is the main cause of extension twins occurring in the edge region. However, the effect of extension twins on micro-hardness is less than that of dislocations. The micro-hardness of both free-end torsion specimens increases almost linearly with increasing distance from center to edge on the cross-section. Nevertheless, the increase in micro-hardness of the pre-tension and then torsion sample is inconspicuous because pre-tension leads to dislocation proliferation and dislocation accumulation saturation. The result also indicates that both pre-tension and free-end torsion can lead to dislocation strengthening, which can obviously increase the micro-hardness and compressive yield stress. The underlying mechanisms were explored and discussed in detail.
在本研究中，利用电子背散射衍射（EBSD）、压缩试验和显微硬度测试，研究了预拉伸对挤压态AZ31镁合金自由端扭转行为、压缩力学性能和显微硬度的影响。结果表明，预拉伸可导致显著的位错强化，这会提高扭转屈服强度，并使预拉伸试样在塑性变形阶段的剪应力-剪应变曲线几乎与挤压态试样的平行。通过自由端扭转，预拉伸试样和挤压态试样横截面边缘位置的织构均可向挤压方向旋转约30°。斯威夫特效应是中心区域出现大量拉伸孪晶的主要原因。相比之下，正应力是边缘区域出现拉伸孪晶的主要原因。然而，拉伸孪晶对显微硬度的影响小于位错。两个自由端扭转试样的显微硬度在横截面上均随距中心到边缘距离的增加几乎呈线性增加。不过，预拉伸后再扭转试样的显微硬度增加不明显，因为预拉伸会导致位错增殖和位错积累饱和。结果还表明，预拉伸和自由端扭转均可导致位错强化，这会显著提高显微硬度和压缩屈服应力。对其潜在机制进行了详细的探索和讨论。
