One of the main degradation mechanisms of the zirconium alloys used in nuclear reactors is hydrogen embrittlement and the formation of zirconium hydrides. This study focuses on understanding the interactions among deformation twins, hydrides, and the microcracks that form within hydrides. For this purpose, in-situ scanning electron microscopy and interrupted ex-situ tensile experiments were conducted on hydrided zirconium specimens with favorable initial textures for the formation of extension twins. Electron backscatter diffraction (EBSD) was used to measure the orientations of the grains located in the specimens’ gauges and map them into a crystal plasticity finite element model to study hydrides and twins interactions. High spatial resolution EBSD and high-resolution imaging were used to follow the formation of microcracks, and twins live. Although the specimens were deformed to a moderate level of applied strain (∼7 %), it was observed that two types of twins nucleate, {101‾2} and {112‾1}. While the former nucleates either before or after the nucleation of microcracks within hydrides, the latter nucleates after the formation of microcracks and grows with them. It is shown that the formation of twins may contribute to crack nucleation, yet the shear energy density on a given slip system within hydrides is the main driving force for crack nucleation. Regardless of hydride interactions with twins, a significant slip activity is recorded within hydrides prior to cracking.

中文翻译：

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变形孪晶、氢化锆和微裂纹的相互作用


核反应堆中使用的锆合金的主要降解机制之一是氢脆和氢化锆的形成。本研究的重点是了解变形孪晶、氢化物和氢化物内部形成的微裂纹之间的相互作用。为此，对具有良好初始织构形成延伸孪晶的氢化锆试样进行了原位扫描电子显微镜和间断非原位拉伸实验。电子背散射衍射 （EBSD） 用于测量位于样品标片中的晶粒的取向，并将它们映射到晶体塑性有限元模型中，以研究氢化物和孪晶的相互作用。高空间分辨率 EBSD 和高分辨率成像用于跟踪微裂纹的形成，双胞胎是活的。尽管标本变形到中等水平的外加应变 （∼7 %），但观察到两种类型的双胞胎成核，{101 ̅2} 和 {112 ̅1}。前者在氢化物内微裂纹成核之前或之后成核，而后者在微裂纹形成后成核并与它们一起生长。结果表明，孪晶的形成可能有助于裂纹成核，但氢化物内给定滑移系统上的剪切能量密度是裂纹成核的主要驱动力。无论氢化物与孪晶的相互作用如何，在开裂之前，氢化物内都会记录到显着的滑移活性。