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MM: Fachverband Metall- und Materialphysik
MM 49: Computational Materials Modelling VII - Grain boundaries & Interfaces
MM 49.2: Talk
Thursday, April 3, 2014, 10:30–10:45, IFW D
Ab-initio study of hydrogen trapping by kappa-carbides in an austenitic Fe matrix — •Poulumi Dey1, Roman Nazarov2, Tilmann Hickel1, and Jörg Neugebauer1 — 1Max-Planck-Institut für Eisenforschung GmbH, D-40237 Düsseldorf, Germany — 2Lawrence Livermore National Laboratory 7000 East Avenue, Livermore, CA 94550
Experimental studies demonstrated that fine dispersed precipitates of carbides increase the tensile strength of steels and may act as deep trapping sites for hydrogen. In this regard, homogeneously distributed nano-sized kappa-carbides (Fe,Mn)3AlC, have been found to play an analogous role in a new class of high strength Fe-Mn-Al-C steels. However, much less is known about the efficiency of these carbides in trapping hydrogen in these steels. We thus perform a quantitative analysis of hydrogen solution enthalpies within kappa-carbide precipitates employing density functional theory (DFT). While the solubility of hydrogen is low in perfect kappa-carbide, the presence of hydrogen makes the formation of vacancies energetically favourable, which inturn act as effective trapping sites for hydrogen. Further, motivated by the experimental investigations, we investigate the trapping of hydrogen at the interface between kappa-carbide and the austenitic matrix. Our results show that the interface is a potential trapping site for hydrogen and also a nucleation point for subsequent fracture in the material.