Berlin 2008 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 47: SYM Hydrogen in Materials: New Developments V

MM 47.3: Talk

Friday, February 29, 2008, 10:55–11:15, H 1058

Hydrogen enhanced local plasticity: An atomistic study — •Johann von Pezold and Jörg Neugebauer — Max Planck Institut fuer Eisenforschung, Duesseldorf, Deutschland

The degradation of metals by H-embrittlement is a long-standing problem of huge economic impact, whose underlying mechanisms are still largely unclear, despite extensive research activities. Based on continuum elasticity theory as well as on experimental evidence, various mechanisms for the observed H-induced embrittlement of metals have been proposed, including stress-induced hydride formation, the HELP (hydrogen enhanced local plasticity) and the HEDE (hydrogen enhanced decohesion) mechanisms. However, the atomistic understanding of these mechanisms is still rudimentary.

In this study we consider the atomistic basis for the HELP mechanism, which is based on the assertion that H enhances the mobility of dislocations by shielding the elastic dislocation-dislocation and dislocation-solute interactions. In order to investigate the underlying atomistic mechanisms, the interaction of edge dislocations in Ni with dissolved H atoms has been studied using molecular dynamics simulations in conjunction with the embedded atom method (EAM).

In particular, the stability of isolated H atoms in the stress field of an edge dislocation, as well as the effect of H atoms on the elastic dislocation-dislocation interaction has been considered. In addition, the effect of H atoms on the velocity of an edge dislocation under the influence of an external stress will be presented.