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MM: Fachverband Metall- und Materialphysik
MM 9: Interfaces II: Segregation and embrittlement
MM 9.2: Talk
Monday, March 7, 2016, 12:00–12:15, H39
Chemical trends in grain-boundary elasticity from ab initio calculations: case study of Σ5(210) Ni3(Al,Si) — •Martin Friák1,2, Monika Všianská2,1, David Holec3, and Mojmír Šob2,1,4 — 1Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Brno, Czech Republic — 2Central European Institute of Technology, CEITEC MU, Masaryk University, Brno, Czech Republic — 3Montanuniversität Leoben, Leoben, Austria — 4Department of Chemistry, Faculty of Science, Masaryk University, Brno, Czech Republic
We employ quantum-mechanical calculations within the density functional theory to study elastic properties of Σ5(210) grain boundaries (GB) in Ni3Al with and without segregated Si atoms substituting Al atoms. Anisotropic elastic properties of 64-atom computational supercells (as periodic approximants of GBs) are determined using the stress-strain method. We compare elastic properties of two chemical compositions of the Σ5(210) GB in Ni3Al with those with Si atoms at different Al positions at this GB. The elastic properties of the Σ5(210) GB Ni3Al grain boundaries are found to be very different from the bulk (they possess orthorhombic symmetry and are softer) and exhibit high sensitivity to the chemistry of the grain-boundary interface and its surrounding atomic neighborhood. This sensitivity is, nevertheless, limited to only a few atomic layers away from the grain boundary. Comparing our quantum-mechanical results with predictions obtained by linear-elasticity approach we demonstrate deficiencies of the latter and thus a clear need to use ab initio methods in this field.