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首页> 外文期刊>ISIJ international >In-situ Microbending Tests of Ni–Cr Alloy during Cathodic Hydrogen Charging by Electrochemical Nanoindentation
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In-situ Microbending Tests of Ni–Cr Alloy during Cathodic Hydrogen Charging by Electrochemical Nanoindentation

机译：电化学纳米压痕法在Ni-Cr合金阴极充氢过程中的原位微弯曲试验

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摘要

To investigate hydrogen embrittlement susceptibility of an individual grain boundary, microcantilevers were fabricated on Ni–Cr bialloy surfaces by focused ion beam, and microbending tests were conducted during hydrogen charging by electrochemical nanoindentation. For microcantilevers fabricated across a twin boundary and inside a grain, no crack was formed by the bending both in air and during hydrogen charging. On the other hand, for microcantilevers fabricated across a random grain boundary, a crack was formed by the bending during hydrogen charging, whereas no crack was formed in air. Thus, it was identified that, for Ni–Cr bialloy, random grain boundaries are more susceptible to hydrogen than twin boundaries and crystalline planes. To validate these experimental results, slow strain-rate tensile tests were also performed, and subcracks of the fractured specimens were analyzed by electron beam back-scattering diffraction. In accordance with the microbending test results, subcracks were predominantly formed along random grain boundaries, but never along twin boundaries and inside grains. Higher hydrogen susceptibility of the random grain boundaries with lower cohesive energy (i.e. , work for separation), smooth fracture surfaces without dimples or tear ridges, and no correlation between strain accumulation and subcrack formation indicate that hydrogen embrittlement of Ni–Cr bialloy is caused by decohesion mechanism, where hydrogen atoms lower cohesive energy at grain boundaries.
机译：为了研究单个晶界的氢脆敏感性，通过聚焦离子束在Ni-Cr双合金表面上制造了微悬臂，并通过电化学纳米压痕在氢充电过程中进行了微弯曲试验。对于在孪晶边界和晶粒内部制造的微悬臂，在空气中和充氢过程中，弯曲都不会形成裂纹。另一方面，对于在随机晶界上制造的微悬臂，在充氢过程中通过弯曲形成裂纹，而在空气中未形成裂纹。因此，可以确定的是，对于镍铬双合金，随机晶界比孪晶界和晶面更容易受到氢的影响。为了验证这些实验结果，还进行了慢应变速率拉伸试验，并通过电子束反向散射衍射分析了断裂样品的亚裂纹。根据微弯曲测试结果，亚裂纹主要沿随机晶界形成，但从未沿双晶界和内部晶界形成。具有较低内聚能的随机晶界的较高氢敏感性（即，用于分离），断裂表面光滑，无凹痕或撕裂脊，应变积累与亚裂纹形成之间没有相关性，表明镍铬双合金的氢脆性这是由于脱粘机理引起的，其中氢原子降低了晶界处的内聚能。

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