ICAMS / Interdisciplinary Centre for Advanced Materials Simulation


Thermodynamic assessment and modelling of ternary Ti–Al systems

Date: 07.05.2013
Time: 11:20 a.m.
Place: ICAMS² 2013, International Colloquium on Advanced Materials Simulation, Bochum, Germany

Damian Cupid, Karlsruher Institut für Technologie, Eggenstein-Leopoldshafen, Germany
Mario Kriegel, TU Bergakademie Freiberg, Freiberg, Germany
Michele Manuel, University of Florida, Gainesville, USA
Hans Seifert, Karlsruher Institut für Technologie, Eggenstein-Leopoldshafen, Germany

Titanium aluminides alloyed with Cr, Moand Nb, respectively, are promising materials for high temperature turbine applications. In comparison to non-alloyed titanium aluminides they show improved high temperature oxidation resistance and good processability.The computer calculations of phase diagrams with consistent thermodynamic databases(CALPHAD approach) can be efficiently used to support such advanced Ti-Al-base alloy development. Additionally, the thermodynamic data are key input for kinetic sharp interface and phase field simulations in ternary systems. Thermodynamic descriptions for Ti–Al-X ternary systems (X: Cr, Mo, Nb) were developed by thermodynamic assessment and optimization. Experimental data from this work as well as literature data on thermodynamics and phaseequilibria were used. Based on this information, analytical descriptions for the Gibbs energies for all stoichiometric and solid solution phases were delivered. Sublattice models described in the Compound Energy Formalism were applied. In all modeling cases the crystal structures and species site occupancies of the related Wyckoff-positions in dependence on alloy compositions and temperature were taken into account. The methods of thermodynamic dataset development will be presented. The calculated thermodynamic results are shown, e.g. by isothermal sections, isopleths, phase fraction diagrams, and chemical potential diagrams. Additionally, all thermodynamic functions in the ternary system can be calculated. Key thermodynamic experiments were defined and carried out to refine the datasets and confirm calculated results.

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