Berlin 2018 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 3: Topical session (Symposium MM): Hydrogen in Materials
MM 3.3: Vortrag
Montag, 12. März 2018, 11:45–12:00, H 0107
Ab-initio study of the role of kappa carbides as potential hydrogen traps in advanced high-strength steels — •Poulumi Dey1, Tobias A. Timmerscheidt2, Dimitri Bogdanovski2, Jörg von Appen2, Tilmann Hickel1, Richard Dronskowski2, and Jörg Neugebauer1 — 1Max-Planck-Institut für Eisenforschung GmbH, D-40237 Düsseldorf, Germany — 2Institute of Inorganic Chemistry, RWTH Aachen University, 52056 Aachen, Germany
Hydrogen embrittlement is one of the major challenges for Fe based materials such as high-Mn steels. Addition of Al to high-Mn steels is known to reduce their sensitivity to hydrogen-induced delayed fracture which motivated us to investigate possible trapping effects related to the presence of Al in the grain interior employing density-functional theory (DFT). The role of Al-based kappa carbide precipitates is investigated to understand the relevance of short-range ordering effects. As H tends to occupy the same positions as C in these precipitates, the interaction and competition between both interstitials is studied via DFT-based simulations. Our study reveals that the interstitials tend to increase the lattice parameter leading to a net increase of the trapping capability despite the fact that the individual H-H/C-H chemical interactions are generally repulsive. An increased Mn content is shown to enhance H trapping due to attractive short-range interactions. Another short-range ordering that is favorable for H trapping is found at the interface between an Fe-matrix and the carbide. The study further shows that the trapped H atoms subsequently yield a decohesion at the interface, which may be one reason for the observed failure.