Regensburg 2016 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 9: Interfaces II: Segregation and embrittlement

MM 9.2: Vortrag

Montag, 7. März 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 Friák^1,2, Monika Všianská^2,1, David Holec³, and Mojmír Šob^2,1,4 — 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.