Cold dwell sensitivity of near α titanium alloys has posed a significant challenge to the engineering safety within the aerospace industry. However, there exists inconsistency regarding the critical facet formation mechanism between basal and prismatic nucleation. A key revelation in this paper is that the controversy surrounding the facet nucleation plane primarily arises from variations in texture: when the loading direction is parallel to the -axis or at a 45 ° angle, it leads to basal plane cracking, whereas loading direction perpendicular to the -axis results in prismatic plane cracking. What's more, a large anisotropy is observed in the dwell fatigue performance in descending order: rolling direction (RD) > transverse direction (TD) >45° direction. To be specific, the dwell fatigue life of RD specimens was 2 times and 4.07 times longer than that of TD and 45 ° specimens, which exhibits excellent dwell fatigue resistance. Furthermore, the high prismatic dislocation density near the facet of RD specimen was confirmed through the Transmission Electron Microscope (TEM) and Transmission Kikuchi Diffraction (TKD) map, which is evidenced that prismatic slips lead to higher strain hardening during cyclic loading. The basal plane of facet grain is generally parallel to the facet line, indicating that the elliptical facet developed by the transgranular fracture through basal plane. Twinning activation in hard grain to accommodate deformation in Ti60 alloy is firstly observed under dwell fatigue tests, which is a product of high stress level in the hard grain. This paper unveils the significant impact of texture on dwell fatigue resistance, offering novel insights into enhancing dwell fatigue performance through texture control.

中文翻译：

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强横向织构钛合金中的裂纹形核和位错活动：增强驻留疲劳抗力的见解

近α钛合金的冷驻敏感性对航空航天工业的工程安全提出了重大挑战。然而，基底成核和棱柱形核之间的关键刻面形成机制存在不一致。本文的一个关键启示是，围绕小平面成核面的争议主要源于织构的变化：当加载方向平行于-轴或成45°角时，会导致基面开裂，而加载方向垂直于-轴时，会导致基面开裂。到 - 轴会导致棱柱面开裂。此外，在驻留疲劳性能中观察到较大的各向异性，按降序排列：轧制方向（RD）>横向（TD）>45°方向。具体而言，RD试件的驻留疲劳寿命分别是TD和45°试件的2倍和4.07倍，表现出优异的驻留疲劳性能。此外，通过透射电子显微镜（TEM）和透射菊池衍射（TKD）图证实了RD样品小面附近的高棱柱位错密度，这证明棱柱滑移导致循环加载期间更高的应变硬化。刻面晶粒的基面总体上与刻面线平行，表明穿晶断裂穿过基面发育成椭圆形刻面。在驻留疲劳试验中首次观察到硬晶粒中孪晶激活以适应 Ti60 合金的变形，这是硬晶粒中高应力水平的产物。本文揭示了织构对驻留疲劳性能的显着影响，为通过织构控制增强驻留疲劳性能提供了新颖的见解。