Dresden 2009 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 18: Mechanical Properties IV
MM 18.3: Vortrag
Dienstag, 24. März 2009, 12:30–12:45, IFW D
Temperature dependence of the stacking fault energy in FeMn alloys: An ab-initio study — •Andrei Reyes-Huamantinco1, Peter Puschnig1, Levente Vitos2, Andrei Ruban2, and Claudia Ambrosch-Draxl1 — 1Chair of Atomistic Modelling and Design of Materials, Department of Materials Physics, University of Leoben, Leoben, Austria — 2Applied Material Physics, Department of Materials Science and Engineering, Royal Institute of Technology, Stockholm, Sweden
The stacking fault energy in Fe-based austenitic alloys (e.g. steels) is an important microscopic parameter that determines the mechanical hardness of the material. Within the axial interaction model it is possible to estimate the stacking fault energy in an fcc crystal from the free energies of the hcp, dhcp (double hcp) and fcc lattices. The vibrational, electronic and magnetic entropy contributions to the free energy have been assessed theoretically, with emphasis on the correct description of the magnetic entropy, in substitutional FeMn binary alloys. Density-functional theory (DFT), the exact muffin-tin orbitals (EMTO) method and the coherent potential approximation (CPA) have been used to calculate the stacking fault energy in random alloys, where simultaneous chemical and magnetic disorder is present. From the analysis of the stacking fault energies as a function of temperature, it is possible to identify the temperatures and Mn concentrations at which the austenitic (fcc) or else the hcp phase is stabilized. The specific role of the disordered local magnetic moments on the stability of FeMn austenitic alloys has been investigated.