International Hydrogen Conference (IHC 2012): Hydrogen-Materials Interactions
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Hydrogen has a strong binding to vacancies, which could lead to large vacancy concentrations. We study, by atomistic simulations, their possible impact on mechanical properties of grain boundaries. Intergranular vacancy clusters are generated by a Monte Carlo (MC) procedure. The MC simulation box is replicated to construct a large bicrystal where a crack is introduced. Increasing loads are applied via Molecular Statics. Crack tip morphologies are analyzed to determine the range of loads where dislocations are emitted and the theoretical load for brittle propagation when emission is switched off. We found the density of clusters that markedly decreases the load for brittle fracture. The conditions for a precise determination of the crossover from intrinsic ductility to brittleness are discussed.