空孔型欠陥のin situおよび二次元分布計測による金属水素脆化支配欠陥

这项研究的主要目的是改进正电子湮没光谱技术，这是检测原子空位的唯一方法，并确认导致氢能基础设施中常见金属氢脆的缺陷，即空位-氢复合体。发展了一种氢环境、氢环境和拉应力下的正电子湮没寿命原位测量方法，并证明了在氢扩散系数很大的纯bcc-Fe中存在空位-氢复合体，这种空位-氢复合体在卸载后由于氢的脱附而在室温老化时变得不稳定。设计了一种聚四氟乙烯电解槽，用于正电子湮没的原位测量。正电子寿命测量是在充电时进行的，这些样品在氢环境中以快应变速率或慢应变速率应变，最高可达25%。与以前的研究一致，在快应变速率下应变的样品的结果表明，无论是在原位充氢过程中还是在空气中，无论测量结果如何，都会形成空位团。另一方面，在慢应变速率下应变的样品中，在充氢过程中检测到空位-氢复合体的形成。随后，由于样品中氢的脱附，随着空气中老化时间的延长，这些缺陷成长为越来越大的空位团。

The main purpose of this research is to improve the positron annihilation spectroscopy technique, which is the only method for detecting atomic vacancies and to obtain confirmation of the defects thought to be responsible of the hydrogen embrittlement in common metals used in the hydrogen energy infrastructure, that is the vacancy-hydrogen complexes. An in-situ positron annihilation lifetime measurement method in a hydrogen environment, as well as in a hydrogen environment and under tensile stress, was developed and the existence of the vacancy-hydrogen complex, which becomes unstable by room temperature aging due to the hydrogen desorption after unloading, was proved in pure bcc-iron, which has a very large hydrogen diffusion coefficient.A Teflon electrolytic cell was devised for in-situ positron annihilation measurements under electrolytic hydrogen addition and stress loading. Positron lifetime measurements were carried out while charging charging the samples that were strained at fast or slow strain rate up to 25% in a hydrogen environment. The results for the sample strained at fast strain rate showed the formation of vacancy clusters irrespective of the measurements during in-situ hydrogen charge or in air, in accordance with previous studies. On the other hand, in the sample strained at slow strain rate the formation of vacancy-hydrogen complexes was detected during the hydrogen charge. Subsequently, these defects grew into increasingly larger vacancy clusters as a function of aging time in air due to the hydrogen desorption from the sample.