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MM: Fachverband Metall- und Materialphysik

MM 16: Structural Materials

MM 16.4: Vortrag

Dienstag, 15. März 2011, 11:45–12:00, IFW D

First principles study of elastic properties of eutectic Ti-Fe alloys up to their mechanical stability limits — •Li-Fang Zhu, Martin Friák, Alexey Dick, Alexander Udyansky, and Jörg Neugebauer — Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Str. 1, 402 37, Düsseldorf, Germany

Ti-based alloys have been suggested for commercial applications due to their high strength and good corrosion resistance. Motivated by experimental results showing eutectic Fe-Ti alloys decomposing into the FeTi compound with B2 structure and beta-Ti(Fe) alloys with varying Ti concentration (depending on the cooling rate), Ti-Fe alloys covering a broad range of Ti concentrations were studied using density functional theory (DFT) within the generalized gradient approximation (GGA). After examining thermodynamic stability and structural properties, ground-state single crystalline elastic constants have been calculated and homogenized in order to determine experimentally accessible elastic moduli. Employing the quasi-harmonic approximation, temperature dependences of single-crystaline and polycrystalline elasticity parameters have been predicted. Further, by simulating tensile tests along [001], [110] and [111] directions, the theoretical tensile strengths have been determined for both FeTi-B2 and beta-Ti(Fe) phases. In addition, the brittle-fracture crystal separation was simulated for (001), (110) and (111) planes. Searching for a loading mode of materials failure, our FeTi-B2 results show that the theoretical tensile strength is lowest along the [001] direction and that the brittle-fracture crystal separation energy is lowest for the (110) plane.