Hydrogen embrittlement jeopardizes the use of high-strength steels in critical load-bearing applications. However, uncertainty regarding how hydrogen affects dislocation motion, owing to the lack of quantitative experimental evidence, hinders our understanding of hydrogen embrittlement. Here, by studying the well-controlled, cyclic, bow-out motions of individual screw dislocations in α-iron, we find that the critical stress for initiating dislocation motion in a 2 Pa electron-beam-excited H₂ atmosphere is 27–43% lower than that in a vacuum environment, proving that hydrogen enhances screw dislocation motion. Moreover, we find that aside from vacuum degassing, cyclic loading and unloading facilitates the de-trapping of hydrogen, allowing the dislocation to regain its hydrogen-free behaviour. These findings at the individual dislocation level can inform hydrogen embrittlement modelling and guide the design of hydrogen-resistant steels.

氢脆会危及高强度钢在关键承重应用中的使用。然而，由于缺乏定量实验证据，氢如何影响位错运动的不确定性阻碍了我们对氢脆的理解。在这里，通过研究 α 铁中单个螺型位错的良好控制、循环、弓形运动，我们发现在 2 Pa 电子束激发的 H 2 中启动位错运动的临界_应力大气比真空环境低 27-43%，证明氢增强螺旋位错运动。此外，我们发现除了真空脱气外，循环加载和卸载有助于氢的脱困，使位错恢复其无氢行为。这些在单个位错水平上的发现可以为氢脆建模提供信息并指导耐氢钢的设计。