Dresden 2020 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 28: Computational Materials Modelling - Hydrogen in metals

MM 28.1: Talk

Tuesday, March 17, 2020, 14:15–14:30, IFW B

Understanding rate dependent hydrogen embrittlement in polycrystalline nickel — •Ali Tehranchi, Tilmann Hickel, and Jörg Neugebauer — Max-Planck-Institut für Eisenforschung GmbH, D-40237 Düsseldorf, Germany

Hydrogen embrittlement (HE) is a persistent mode of failure in metals. It is well known that hydrogen decreases the fracture energy of grain boundaries (GBs) and promotes intergranular fracture. Hydrogen also increases the critical stress for dislocation-GB reactions. As a consequence, more populated pile-ups of the dislocations will form near the GBs. The dislocations in these pile-ups can attract more hydrogen atoms due to their stress field and deliver them to the GB and facilitate the formation of intergranular crack nuclei. If the length of the crack nucleus is larger than a certain critical length it can propagate along the GB without any need for long-range diffusion of H atoms from the bulk, causing embrittlement. In this work, atomistic simulations of the dislocation-GB interactions are used to demonstrate the increase in the critical stress. The energetics and kinetics of the population of the hydrogen atoms around the dislocation pile-up are presented and discussed. A criterion for fast intergranular fracture is given. This criterion explains the rate dependent experimental observations of HE in nickel as a representative fcc metal. The proposed framework is general and can be used for the prediction of HE in other metallic polycrystals.