Abstract It is generally believed that the H-induced reduction in dislocation energy plays a key role in modifying dislocation behaviors in the process of hydrogen embrittlement. Here, we examine the factors that lead to H reducing the line energies of the edge and screw dislocations in bcc Fe by atomistic simulations. Grand canonical Monte Carlo simulations are conducted to obtain the distribution of H around the dislocations. We find that H mainly aggregates at the dislocation cores and the H concentration in the elastic field of dislocations is extremely low. The direct consequences of such a distribution pattern of H are as follows. (i) In contrast with previous studies, H induces no change in the shear modulus of the systems containing dislocations. (ii) H increases the core radii and decreases the core energies of the dislocations, which are the only factors leading to the reduction of dislocation line energy by H. (iii) H brings little effect on the stress field of either the edge or screw dislocation, implying that H induces almost no stress-shielding effect on dislocations. A linear relation between the critical shear stress for homogeneous dislocation nucleation and logarithmic bulk H concentration is thus revealed, based on the atomistic result of the H-induced increase in the core radius and decrease in the core energy of the dislocations. The present results indicate that the dislocation-dislocation interaction in the presence of H, which is the key ingredient for the H-enhanced localized plasticity mechanism for hydrogen embrittlement, can be easily evaluated by the linear elastic theory of dislocations if the core radius and energy of dislocations are properly described.

中文翻译：

---

位错核半径和能量在氢与位错相互作用中的关键作用

摘要 一般认为，氢致位错能的降低在改变氢脆过程中的位错行为中起关键作用。在这里，我们通过原子模拟检查导致 H 降低 bcc Fe 中边缘和螺旋位错的线能量的因素。进行正则蒙特卡罗模拟以获得位错周围的 H 分布。我们发现 H 主要聚集在位错核心处，位错弹性场中的 H 浓度极低。H 的这种分布模式的直接后果如下。(i) 与之前的研究相比，H 不会引起包含位错的系统的剪切模量发生变化。(ii) H 增加核心半径并降低位错的核心能量，这是导致位错线能量降低的唯一因素。 (iii) H 对边缘位错或螺旋位错的应力场几乎没有影响，这意味着 H 对位错几乎没有应力屏蔽效应。因此，基于 H 诱导的核心半径增加和位错核心能量降低的原子学结果，揭示了均匀位错成核的临界剪切应力与对数体积 H 浓度之间的线性关系。目前的结果表明，在 H 存在下的位错-位错相互作用，H 是 H 增强的氢脆局部塑性机制的关键因素，