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Mapping TCP multiphase stability by coupling first-priciples energetics to Gibbs thermodynamics

Suzana Fries, Ruhr-Universität Bochum, Bochum, Germany

Mauro Palumbo, Ruhr-Universität Bochum, Bochum, Germany

Alvin Ladines, Ruhr-Universität Bochum, Bochum, Germany

Thomas Hammerschmidt, Ruhr-Universität Bochum, Bochum, Germany

Ralf Drautz, Ruhr-Universität Bochum, Bochum, Germany

Time & Place
  • Date: 09.09.2012
  • Time:
  • Place: The 14th International IUPAC Conference on High Temperature Materials Chemistry, University of Science and Technology, Bejing, China

Abstract

High temperature applications need materials with excellent thermo-physical and mechanical properties which should be part of the pre-production design in order to assure energy sustainability including processing and use. Examples of such materials are steels and Ni-/Co-base superalloys. In these systems the topologically close-packed (TCP) phases play a role as both, stable and metastable phases. We created a thermodynamic database using the as-calculated density functional theory (DFT) configurational energies [1] of formation for several TCP forming systems in combination with a CALPHAD format [2] in order to calculate stable and metastable phase diagrams.

The results of multiphase equilibria calculated using a Gibbs energy minimiser, like driving forces for precipitation, volumes, heat-capacities (considering only Bragg-Williams-Gorsky configuration entropy), etc, can be exported to processing and aging like microstructure simulations and creep.

Here, we present phase diagrams for fcc, bcc, and hcp families of structures including the TCP phases A15, C14, C15, C36, σ, μ and χ.

[1] B. Seiser, T. Hammerschmidt, A.N. Kolmogorov, R. Drautz and D.G. Pettifor, Phys. Rev. B 83, 224116 (2011)
[2] M. Palumbo, T. Abe, S.G. Fries and A. Pasturel, Phys. Rev. B 83, 144109 (2011)

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