Effect of texture and banded structure on the crack initiation mechanism of a friction stir welded magnesium alloy joint in very high cycle fatigue regime
Effect of texture and banded structure on the crack initiation mechanism of a friction stir welded magnesium alloy joint in very high cycle fatigue regime
复制标题
织构和带状结构对高周疲劳状态下搅拌摩擦焊镁合金接头裂纹萌生机制的影响
DOI：
10.1016/j.ijfatigue.2020.105617
复制
发表时间：
2020-07-01
影响因子：
6
通讯作者：
Liu, Yongjie
中科院分区：
文献类型：
--
作者：
Chen, Yao;Zhang, Ruofan;Liu, Yongjie
搅拌摩擦焊接头熔核区存在非均匀组织，这将影响接头的疲劳响应。揭示了镁合金搅拌摩擦焊接头的独特织构和带状组织及其对裂纹萌生行为的决定性作用。在较高的应力水平下，由于边界附近的不均匀变形，失效沿着AS NZ/TMAZ边界（AS：前进侧，NZ：熔核区，TMAZ：热机械影响区）发生。严重的塑性变形集中在带状组织的较软层。但在较低应力水平下，塑性变形变得微弱和局部化，但由于软织构取向相同，塑性变形在带状组织的交替层中同时累积，并导致带状组织的随机失效。通过半定量力学模型验证了失效机理。
Friction stir welding (FSW) produces heterogeneous microstructure in nugget zone of its joint, which should affect the fatigue responses. This work revealed the unique texture and banded structure of the Mg-FSW joint and their decisive roles on crack initiation behaviors. At higher stress levels, failures occur along the AS NZ/TMAZ boundary (AS: advancing side, NZ: nugget zone, TMAZ: thermo-mechanically affected zone) due to the inhomogeneous deformations near the boundary. Severe plastic deformations concentrate in the softer layers of banded structure. However, at lower stress levels, plastic deformations become weak and localized, but accumulate in the alternate layers of banded structure simultaneously due to the same soft texture orientation, and induce random failures in banded structure. The failure mechanisms are verified by semi-quantitative mechanical models.