Dresden 2014 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 15: Computational Materials Modelling III - Bulk thermodynamics/ Phase Transitions I

MM 15.3: Vortrag

Montag, 31. März 2014, 16:15–16:30, IFW D

Influence of magnetism on the stability of binary transition-metal compounds — •Alvin Noe Ladines, Thomas Hammerschmidt, and Ralf Drautz — ICAMS, Ruhr Universität Bochum, Germany

Refractory elements (RE) play an important role in the development of creep-resistant ferritic steels for high temperature applications. They can act as solid solution strengthener or carbide-former but also lead to the precipitation of topologically close-packed (TCP) phases that may initiate embrittlement and fracture. It is thus important to predict the formation of TCP phases in multi-component alloys. An attempt to address this is the development of structure maps which relate the alloy stability to atomic-size difference and average band-filling of the constituents. In this study we quantify the influence of magnetism for a recently developed structure map for TCP phases of transition-metal compounds. Based on density functional theory (DFT) calculations of the heat-of-formation of TCP phases in several Fe-RE systems over the whole range of chemical composition, we derive a model that correlates the magnetic energy to the average band filling of the compounds. This can be understood within the Stoner model of itinerant magnetism where the magnetic moment on the atom corresponds to a rigid shift in the spin-polarized density of states. We rescale the structure map with respect to this shift.