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MM: Fachverband Metall- und Materialphysik

MM 36: Topical Session Electron Theory V

MM 36.6: Vortrag

Donnerstag, 17. März 2011, 15:45–16:00, IFW A

Temperature dependence of the stacking fault energy in Fe_0.716Cr_0.200Ni_0.084 alloy from first principles — •Hojjat Gholizadeh^1,2, Andrei Reyes-Huamantinco^1,2, Andrei Ruban³, Peter Puschnig¹, and Claudia Ambrosch-Draxl¹ — ¹Chair of Atomistic Modelling and Design of Materials, University of Leoben, Austria — ²Materials Center Leoben, Austria — ³Applied Material Physics, Royal Institute of Technology, Stockholm, Sweden

The mechanism of plastic deformation of steels under mechanical stress is governed by the magnitude of the stacking fault energy (SFE). We calculate the SFE for Fe_0.716Cr_0.200Ni_0.084 random alloy in paramagnetic austenitic phase in the temperature range 300-1500 K. Our methodology uses the axial interaction (ANNNI) model to calculate the SFE as a function of the free energies of the perfect fcc, hcp, and double-hcp crystal phases. These free energies are dependent on the lattice parameter which is obtained from experimental thermal expansion data, and on the local magnetic moments which are evaluated using DFT calculations and a Monte-Carlo simulation of a magnetic Hamiltonian of independent local moments. The DFT calculations are performed using the exact muffin-tin orbitals (EMTO) method, which enables to use the coherent potential approximation (CPA) and the disordered local moment (DLM) approaches to model the random alloy in paramagnetic state. Our results, in particular the SFE(T=300 K)=15 mJ/m² and the hcp↔fcc transition temperature of 550 K, are in good agreement with experiments.