In this work, Ti60 alloys with different micro-texture intensity were designed to elucidate the effect of micro-texture on fatigue life and dwell sensitivity and the difference in crack initiation mechanism for low-cycle fatigue (LCF) and dwell fatigue (DF). It was found that micro-texture region (MTR) significantly reduced LCF and DF lifetimes and increased dwell sensitivity compared to no-MTR samples. However, micro-texture does not change the characteristics of the crack initiation grains, and the fracture initiation region facet of all samples matches the (0001) basal plane and is related to basal slip. Therefore, the [0001] orientation domains for crack initiation in both fatigue states are discussed, and it is found that LCF tends to nucleate along the basal slip bands or basal twist grain boundaries (BTGBs) of the high SF grains, whereas DF nucleation is independent of the basal SF value, and the mechanism of initiation of hard oriented grain cracking is also included. In situ further demonstrated that hard grains can activate basal slip as well as cracking, and the possibility of soft/hard grain pairs generating dislocation pile-up stresses leading to cracking of hard grains was determined by theoretical calculations, providing experimental support and evidence for the soft/hard grain model. Based on these findings, criteria for the angle (θ) of the c-axis with respect to the loading axis and the basal SF range are proposed to determine the differences between LCF and DF with respect to the mechanisms of hard grain cracking and BTGB crack initiation.

中文翻译：

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不同驻留敏感性的微织构 Ti60 合金在疲劳和驻留疲劳载荷作用下的裂纹萌生机制

在这项工作中，设计了具有不同微观织构强度的Ti60合金，以阐明微观织构对疲劳寿命和驻留敏感性的影响以及低周疲劳（LCF）和驻留疲劳（DF）裂纹萌生机制的差异。研究发现，与无 MTR 样品相比，微纹理区域 (MTR) 显着缩短了 LCF 和 DF 寿命，并提高了驻留灵敏度。然而，微观织构并没有改变裂纹萌生晶粒的特征，并且所有样品的断裂萌生区面均与（0001）基面匹配，并且与基面滑移有关。因此，讨论了两种疲劳状态下裂纹萌生的[0001]取向域，发现LCF倾向于沿着高SF晶粒的基础滑移带或基础扭曲晶界（BTGB）成核，而DF成核则为与基础 SF 值无关，并且还包括硬取向晶粒裂纹的引发机制。原位进一步证明了硬质晶粒可以激活基底滑移和开裂，并通过理论计算确定了软硬晶粒对产生位错堆积应力导致硬质晶粒开裂的可能性，为该理论提供了实验支持和证据。软/硬颗粒模型。基于这些发现，提出了 c 轴相对于载荷轴的角度 (θ) 和基础 SF 范围的标准，以确定 LCF 和 DF 在硬晶粒裂纹和 BTGB 裂纹机制方面的差异引发。