Relations between Parameters in Different Sublattice Configurations for CALPHAD-Type Thermodynamic Assessments

Abstract

For interstitial solid solutions various sublattice configurations have been applied in CALPHAD-type thermodynamic assessments. To construct a thermodynamic database for multi-component systems from the assessed binary and ternary systems, one difficulty is consistency of the thermodynamic models for those phases with sublattices. Previously, to combine parameters of the different sublattice configurations for the same phase, the thermodynamic assessment would need to be repeated. In the present work, we propose a simple method to convert parameters between the different sublattice configurations and demonstrate that the present parameter conversions work well for the Al-B, C-Fe, and O-Ti binary systems. Although it is a simple conversion process utilizing the known parameters, for the case where the valid composition range is limited, the thermodynamic database can be determined for multi-component systems. Furthermore, if a reassessment is required the conversion can be used to estimate initial values for the parameter optimization.