Thermodynamic properties of Ni–Hf melts

Abstract

Isoperibolic calorimetry is used to determine the integral and partial mixing enthalpies of Ni–Hf melts at 1770 ± 5 K. It is established that Ni–Hf melts form with release of a great amount of heat. Temperature dependence of mixing enthalpies for binary Ni–Hf melts is established. Activities of the melt components are determined from coordinates of the liquidus lines in the phase diagram of this system. The calculated and experimental activities of the Ni–Hf melt components agree well. These data and the mixing enthalpies are used to calculate the Gibbs energies and mixing entropies of Ni–Hf melts. It is shown that they are negative and their absolute value is high.