Fatigue Characterization of Ultrahigh Strength and Ductile Mg-Gd-Y-Zn-Zr Alloy with Hierarchical Anisotropic Nanostructure

研究了长周期有序堆积相镁合金的高周疲劳行为。疲劳断裂和损伤观察表明，微裂纹从较厚的α - mg层形成，远离致密的LPSO片层。值得注意的是，在局部化的氧化物内部观察到微裂纹形核。这项研究强调了高度局域化的氧化物增厚在微裂纹成核过程中的关键作用，它比原生氧化物厚几个数量级。提出的模型重申了挤压/侵入过程的重要性，但更重要的是强调了疲劳诱导氧化导致挤压/侵入结构脆化的机制，这反过来又影响微裂纹的形核。

We investigated the very high cycle fatigue behavior of a Mg alloy with long-period stacking ordered (LPSO) phase. Fatigue fracture and damage observation revealed that microcracks nucleate from the thick alpha-Mg layers, away from the dense LPSO lamellae. Notably, microcrack nucleation was observed inside the localized oxides. This investigation highlights the critical role of highly localized oxide thickening, orders of magnitude thicker than native oxide, in the process of microcrack nucleation. The proposed model reaffirms the importance of the extrusion/intrusion process, but more importantly highlights a mechanism in which fatigue-induced oxidation results in the embrittlement of the extrusion/intrusion structure, which in turn affects the nucleation of microcracks.