Twinning Deformation and Yield Asymmetry Improvement of Magnesium Alloys by Free-End Torsion
Twinning Deformation and Yield Asymmetry Improvement of Magnesium Alloys by Free-End Torsion
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DOI：
10.1007/s11665-023-08854-w
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发表时间：
2023-10
影响因子：
2.3
通讯作者：
Hongbing Chen;Zhikang Shen;Bo Song;Jia She
中科院分区：
文献类型：
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作者：
Hongbing Chen;Zhikang Shen;Bo Song;Jia She
在本研究中，挤压镁银合金棒在室温下承受自由端扭转。结果表明，棒材横向表面中心区伸展孪晶的激活不是由自由端扭转引起的剪应力或正应力引起的，而是由Swift效应引起的压应力引起的。相反，边缘区域的伸展孪晶的激活是由于法向应力而不是剪应力。由于剪切应力的内在线性增加，自由端扭转会导致横向表面上从中心到边缘的位错密度逐渐增加，从而逐渐增加显微硬度。此外，由于脱孪晶和非基滑移主导的拉伸变形的软化效应，自由端扭转可以使TYS略有增加，但由于位错强化和孪晶界强化，自由端扭转也可以显著增加CyS。此外，自由端扭转对极限强度和延伸率的影响可以忽略不计。结果表明，自由端扭转可以在不牺牲极限强度和塑性的前提下，显著改善挤压镁银合金棒的拉压屈服不对称性。
In this investigation, extruded Mg-Ag alloy rods were subjected to free-end torsion at room temperature. The results reveal that the activation of extension twinning in the central area on the transverse surface of the rod is not induced by the shear stress or the normal stress via free-end torsion but by the compressive stress via the Swift effect. In contrast, the activation of extension twinning in the edge area is due to the normal stress rather than the shear stress. Due to the shear stress intrinsic linear increase, free-end torsion can cause a gradual increase in dislocation density from the center to the edge on the transverse surface, which gradually increases the microhardness. Furthermore, free-end torsion can slightly increase the TYS owing to the softening effect of detwinning and nonbasal slip dominated tensile deformation, but free-end torsion can also significantly increase the CYS due to dislocation strengthening and twinning boundary strengthening. Additionally, the effects of free-end torsion on ultimate strength and elongation are negligible. As a result, free-end torsion can significantly improve the tension-compression yield asymmetry of extruded Mg-Ag alloy rods without sacrificing ultimate strength and plasticity.