The thermodynamic properties of α-, σ-, δ- and β- phase Co-Cr alloys have been determined by solidelectrolyte emf and high-temperature calorimetric techniques. The experimental enthalpies and Gibbs energies of formation for each phase have been combined through the equation ∆G = ∆H – T∆S to calculate the corresponding entropies of formation at selected temperatures. Assessed thermodynamic values for Co-Cr alloys are presented and have been used to calculate equilibrium phase boundaries for this system. The calculated boundaries are compared with the published phase boundaries, determined by conventional metallographic methods.
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