Hydrogen Effects on the Migration of Nanoscale Cavities in Iron

Abstract

Accurate knowledge of the influence of hydrogen on the behavior of vacancies and vacancy clusters is crucial for understanding the mechanism of hydrogen embrittlement of α-iron and its alloys. Using in-situ transmission electron microscopy, we examined the effects of hydrogen on the behavior of nanoscale cavities under heating, by comparison between the behaviors of cavities without hydrogen produced upon high-energy electron irradiation and those with hydrogen produced upon electro-deposition. It is revealed that hydrogen promotes the migration of cavities, in contrast to a traditional notion.

Accelerating off-lattice kinetic Monte Carlo simulations to predict hydrogen vacancy-cluster interactions in $α$-Fe

“…It has also been found that the interaction between H and vacancy-clusters has not followed the pattern if extrapolating from V 1 H; perhaps the most interesting behaviour is the reduction in diffusion barrier, upon introduction of H into the larger clusters V 4 H and V 5 H. A similar phenomenon, dubbed the hydrogen lubrication effect, has been explored computationally in FCC metals [80]. If this trend continues and the gap continues to increase, it could help to explain the experimentally observed H-induced nano-void migration [81] and could have implications for HE by contributing towards vacancy agglomeration during the HESIV mechanism [14,82,83]. A similar atomic mechanism that lowers the diffusion barrier for Vacancy-H complexes could be responsible for the predicted increase in dislocation velocity/mobility [84,85], which could directly support the HELP mechanism [9] of HE.…”

Nucleation of Nano-sized Prismatic Dislocation Loop from Spherical Vacancy Clusters in <i>α</i>-iron: An Atomic-scale Study

“…As a result, the fracture process is significantly influenced by vacancies, representing a crucial and decisive factor from this perspective 11,12) . Moreover, the recent study investigated the relationship between local H concentration and vacancy formation energies, focusing on the observed phenomenon of superabundant vacancy formation 13) . It was found that regions characterized by high hydrogen concentrations demonstrated significantly reduced vacancy formation energies, providing support for the experimentally observed superabundance of vacancies.…”