Thermodynamic constraints to describe Gibbs energies for binary alloys

Thermodynamic constraints are introduced to describe Gibbs energies for a C ALPHAD-type calculation; available data on the pure elements and phase diag ram data were used to optimize relevant parameters. Constraints can be appl ied to the mathematical description of Gibbs energies for three regions of phase diagrams: those with complete miscibility: those with an intermetalli c compound, and those with a miscibility gap. The authors examine the prese nt thermodynamic constraints in construction of Gibbs energies for the Ag-P d, Mg-Sn, and Au-Ni binary systems as typical examples for these cases. The optimization procedure for obtaining parameters for models of the Gibbs en ergies is divided mainly into four steps to reach the final parameters, and the results obtained in each step are compared in detail. The authors also present assessed parameters for the Gibbs energies concerning these three binary systems by the available thermodynamic data in addition to the phase diagram data with the present thermodynamic constraints.