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MM: Fachverband Metall- und Materialphysik
MM 49: Computational Materials Modelling VII - Grain boundaries & Interfaces
MM 49.1: Talk
Thursday, April 3, 2014, 10:15–10:30, IFW D
Theoretical study of hydrogen trapping and diffusion at grain boundaries in nickel — •Davide Di Stefano1, Matous Mrovec1,2, and Christian Elsaesser1,2 — 1Fraunhofer IWM, Freiburg, Germany — 2Karlsruhe Institute of Technology, Karlsruhe, Germany
A correct description of hydrogen diffusion in metals is a prerequisite for understanding the phenomenon of hydrogen embrittlement. It is known that H mobility in metals is strongly affected by lattice defects such as vacancies, dislocations or grain boundaries. It is however rather difficult to investigate local diffusion and trapping of H at these nanoscale defects by experimental means.
In this theoretical study, we explore the interaction of H with several grain boundaries (GBs) in Ni at the atomic scale using first principles calculations based on density functional theory (DFT). Our results are that GBs with open structural units act as trapping sites for H and provide also easy diffusion pathways for H. In contrast, GBs with close-packed structures similar to that of bulk fcc Ni do not trap H but act instead as barriers for H. In order to obtain information about H diffusion on long time and length scales, we developed a kinetic Monte Carlo model that can utilize the DFT results to calculate effective diffusion coefficients of polycrystalline microstructure.