Just another WordPress site - Ruhr-Universität Bochum

Abstract

A correct description of hydrogen diffusion and trapping is prerequisite for understanding the phenomenon of hydrogen embrittlement. The macroscopic H diffusion in bulk materials has been studied extensively in the past both experimentally and theoretically. Nevertheless, the knowledge of microscopic diffusion processes, especially in distorted environments around crystal defects, is still limited. We have employed extensive atomistic simulations to investigate the diffusion and trapping of hydrogen in technologically important transition metals such as Fe and Ni using accurate first-principles methods based on the density functional theory as well as large-scale molecular dynamics simulations with classical interatomic potentials. Our results show that the diffusion barriers and traping energies can indeed vary significantly in the vicinity of crystal defects, imperfections and interfaces. The calculations also confirm that a proper treatment of quantum effects is crucial for a reliable theoretical description of H diffusion, in particular for bcc Fe. Several examples of H trapping at dislocations, grain and phase boundaries will be presented and analysed together with the influence of H on the structural and cohesive properties and associated damage mechanisms.