Abstract 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.

中文翻译：

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织构和带状结构对搅拌摩擦焊镁合金超高周疲劳状态下裂纹萌生机制的影响

摘要 搅拌摩擦焊（FSW）在其接头的熔核区产生不均匀的微观结构，这会影响疲劳响应。这项工作揭示了 Mg-FSW 接头的独特织构和带状结构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，沿 AS NZ/TMAZ 边界（AS：推进侧，NZ：熔核区，TMAZ：热机械影响区）发生故障。严重的塑性变形集中在带状结构的较软层中。然而，在较低的应力水平下，塑性变形变弱且局部化，但由于相同的软纹理取向，同时在带状结构的交替层中累积，并导致带状结构的随机失效。