This study utilized transmission electron microscopy (TEM) and on-axis transmission Kikuchi diffraction (TKD) to investigate the fatigue-induced HCP-to-FCC phase transformation in industrial pure zirconium under a stress ratio of R = 0.1. The results show that fatigue damages result from phase deformations during cyclic loadings. The fatigue-induced FCC-Zr phases exhibit a B-type orientation relationship with the HCP-Zr matrix. Notedly, due to the different growth directions of Shockley partial dislocations relative to nucleation points, there are two FCC-Zr variants after the HCP-to-FCC phase transformation. The content of these two variants accounts for 65% and 35% of the total FCC-Zr, respectively, appearing as lamellae morphology embedded parallelly within the matrix. The distribution of the two variants includes isolated distribution and adjacent distribution. For the adjacent distribution, a twinning relationship is observed between the two variants. Meanwhile, as an intermediate transition stage of the HCP-to-FCC phase transformation, stacking faults are observed at the boundaries of the FCC-Zr lamellae. These findings offer insights into the microstructural features and formation mechanisms of fatigue-induced HCP-to-FCC phase transformation.

中文翻译：

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疲劳诱导的 HCP 到 FCC 相变导致纯锆中产生两种 FCC-Zr 变体

本研究利用透射电子显微镜 (TEM) 和同轴透射菊池衍射 (TKD) 研究了工业纯锆在 R = 0.1 的应力比下疲劳引起的 HCP 到 FCC 相变。结果表明，疲劳损伤是由循环载荷期间的相变形引起的。疲劳诱导的 FCC-Zr 相与 HCP-Zr 基体呈现 B 型取向关系。值得注意的是，由于肖克利部分位错相对于成核点的生长方向不同，HCP-to-FCC相变后存在两种FCC-Zr变体。这两种变体的含量分别占FCC-Zr总量的65%和35%，表现为平行嵌入基体中的片晶形态。两种变体的分布包括孤立分布和邻近分布。对于相邻分布，在两个变体之间观察到孪生关系。同时，作为 HCP 到 FCC 相变的中间过渡阶段，在 FCC-Zr 片晶的边界处观察到堆垛层错。这些发现为疲劳引起的 HCP 到 FCC 相变的微观结构特征和形成机制提供了见解。