We conduct in situ tensile straining experiments to investigate the role of hydrogen and slip in crack initiation in nickel-based alloy 725. Our experiments reveal no tendency for hydrogen to enhance localized slip and no necessity of slip for crack initiation. We use electrochemical charging to introduce hydrogen into samples, melt extraction to measure hydrogen content, and digital image correlation to analyze localized plastic strains during in situ tensile tests in a scanning electron microscope. Cracks initiate both in regions with and without nearby localized slip. Moreover, the fraction of cracks initiating with no nearby slip is greater at higher hydrogen content. Slip-assisted crack initiation generally occurs at locations where intergranular slip is arrested, especially at intersections of slipping coherent twin boundaries with thin twin lamellae. Cracks that initiate without nearby slip occur at a wider variety of microstructural features, including inclusions, triple junctions, and surface flaws.

中文翻译：

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滑移在镍基合金 725 氢辅助裂纹萌生中的作用


我们进行了原位拉伸应变实验，以研究氢和滑移在镍基合金 725 裂纹萌生中的作用。我们的实验表明，氢没有增强局部滑移的趋势，也不需要滑移来引发裂纹。我们使用电化学充电将氢引入样品中，使用熔体萃取来测量氢含量，并使用数字图像关联来分析扫描电子显微镜原位拉伸测试期间的局部塑性应变。裂缝会在附近有或没有局部滑移的区域中产生。此外，氢含量越高，在附近没有滑移的情况下引发的裂纹的比例就越大。滑移辅助裂纹萌生通常发生在晶间滑移被阻止的位置，特别是在滑移相干孪晶边界与薄孪晶片层的交叉处。在没有附近滑移的情况下引发的裂纹发生在更广泛的微观结构特征中，包括夹杂物、三重连接和表面缺陷。