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O: Fachverband Oberflächenphysik
O 67: Metal surfaces: Adsorption of H/O and inorganic molecules
O 67.3: Talk
Thursday, March 29, 2012, 11:00–11:15, MA 043
Ab-initio study of the stability of Fe3Al surfaces in contact with an oxygen atmosphere — •Afshin Izanlou, Mira Todorova, Martin Friak, and Jörg Neugebauer — Department for Computational Materials Design, Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf
Iron-aluminides are potential candidates for high temperature applications, but their deformability, which is necessary for manufacturing processes, is reduced by hydrogen diffusion at room temperature. The presence of passive surface films has been reported to reduce H embrittelment [1] by lowering the H liberation rate at the surface. It has been further suggested that addition of passivity inducing alloying elements would have a beneficial effect on their thermo-mechanical and electro-chemical behaviour, as well [2].
In a first step towards the identification of suitable alloying elements that reduce H liberation over a wide range of environmental conditions, we study by density functional theory both clean and oxygen covered low index Fe3Al surfaces. We find the mixed FeAl termination to be most stable on the [001] and [110] clean surfaces, while an Fe-termination is most favourable on the [111] surface. Having identified the likely clean surface terminations, we study low coverage oxygen structures and assess the impact the environment has on surface structure and stability by employing thermodynamic concepts.
[1] C.T. Liu et al., Scr. Metall. Mater. 24 (1990) 385.
[2] R. Balasubramaniam, Bull. Mater. Sci. 3 (1999) 571; D.G. Morris and M. A. Muñoz-Morris, Adv. Eng.Mater., 13 (2011) 43.