Dresden 2011 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 10: Computational Materials Modelling III

MM 10.3: Vortrag

Montag, 14. März 2011, 16:15–16:30, IFW B

DFT study of impurities at grain boundaries in α-Fe — Elwira Wachowicz and •Adam Kiejna — Institute of Experimental Physics, University of Wrocław, Wrocław, Poland

The effects of several metalloid (B), metalloid-like (C, P) and nonmetallic impurities (N, O and S) on structure, energetics and mechanical properties of Σ3 (111) and Σ5 (210) grain boundaries (GBs) in ferromagnetic α-Fe have been studied by density functional theory and the projector augmented wave method. Two different concentrations and positions of impurity atoms at the GB were considered. Most of the impurities enhance the relaxation of the interplanar spacing of the pure grains. Interstitial impurities at both GBs increase separation of the grains while substitutional ones in general either do not alter or decrease it. Segregation of impurity atoms at the GBs and their embrittling/strengthening effect is explored and discussed in terms of its chemical and mechanical components. At the Σ5 GB for all impurity atoms considered the positions in the boundary layer are energetically favored independently of interstitial or substitutional site, whereas the enrichment of the Σ3 GB is favored for the impurities of the interstitial sites as well as for a substitutional P and C. In most cases, impurity atoms both in interstitial and substitutional positions at GBs act as embrittlers. The magnetic moments on the impurities are very small and in most cases align antiparallel to the moments on the neighboring Fe atoms.