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Abstract

Modern multi-phase field models [1-4] rely on thermodynamic and kinetic properties stored in CALPHAD databases. The data has to be retrieved via internal or external minimization if phases are modelled with sublattices and additional degrees of freedom. Recently, an extension to the phase-field model with finite interface dissipation [3-4] has been developed, which models sublattice occupancy not only in a single phase [5], but also between thermodynamic phases overlapping in the diffuse interface. The additional measures will be presented to cope with this situation under the constraint to conserve the total composition, which is calculated from the phasesite- fractions. Nevertheless, with given phase-site-fractions, temperature and pressure, the thermodynamic and kinetic properties and its derivatives can be calculated not only analytically, but also by said external modules like OpenCalphad and Thermo-Calc to ease simulation setups. Further implications for long- and short-range diffusion rigorously on each sublattice according to [6] will be discussed. Finally case studies using internal and external sublattice minimization will be presented to elucidate the effectiveness of the approach.

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