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MM: Fachverband Metall- und Materialphysik

MM 41: Computational Materials Modelling VI - Dislocations

MM 41.3: Vortrag

Mittwoch, 2. April 2014, 12:00–12:15, IFW D

Understanding H-embrittlement on the atomic scale: Multiscale modeling of homogenous dislocation nucleation — •Gerard Leyson, Blazej Grabowski, and Jörg Neugebauer — Max-Planck-Straße 1, 40237 Düsseldorf, Germany

Hydrogen enhanced local plasticity (HELP) is one of the proposed mechanisms by which hydrogen induces embrittlement in metals. A promising methodology to explore the HELP mechanism is through nano-indentation experiments, wherein the effect of hydrogen on the pop-in load is precisely measured. Using the Ni-H system as a model system, an analytic model is developed to quantify the effect of hydrogen on the Homogenous Dislocation Nucleation (HDN) assumed to be responsible for the reduction of the pop-in load. The model takes atomisitic inputs, such as hydrogen-hydrogen interaction and the effect of realistic dislocation cores, into account. The hydrogen binding energy and the local hydrogen concentration were calculated self-consistently. Unlike previous analyses, the model takes into account the complex nature of the dislocation field around the loops, as well as the discrete nature of the atomic lattice. In doing so, it addresses some short-comings of previous models stemming from the continuum description of the dislocation line energy and the interaction of the dislocation with the external stress field. The onset of HDN as a function of bulk hydrogen concentration and temperature was quantified. Our results show that about 10-100 H atoms are sufficient to stabilize a dislocation loop in the presence of realistic shear stresses and allows for a quantitative description of the experimentally observed pop-in effects.