Multiscale simulations of H embrittlement in metals: Application to the HELP mechanism
The prospect of a hydrogen-based economy critically depends on the availability of structural materials that can withstand extended exposure to hydrogen. Most metals, and in particular high strength steels, embrittle under the influence of hydrogen, which results in the catastrophic failure of the material. A number of mechanisms have been proposed to account for the phenomenon, including the hydrogen enhanced decohesion (HEDE) mechanism, the hydrogen enhanced local plasticity (HELP) mechanism and the stress-induced hydride formation mechanism, to name just the most frequently cited ones.In this project we aim to critically assess the different mechanisms from the fundamental quantum mechanical level up to the mesoscopic length-scale employing a hierarchical simulation strategy. At the most fundamental level, ab-initio electronic structure methods are used to characterize the metal-H interaction in various metal hosts. Microstructural aspects of the embrittlement process, such as the segregation of H to extended defects like dislocations and grain boundaries, are addressed using semi-empirical (EAM) interaction potentials, which are validated by reference to the ab-initio determined interaction parameters. Finally, in order to extend the accessible length and time scales of our simulations these data are used to parametrize Ginzburg-Landau type models that allow us to consistently describe the dislocation dynamics and the diffusive time-scale of the H diffusion.