Interactions in Fe-Hf and Ni-Hf melts

The thermochemical properties of Fe-Hf (1870 K) and Ni-Hf (1877 K) melts we re studied by calorimetry. The melts were shown to feature strong interatom ic interactions, with <(Delta H)over bar>(Hf(Fe)) = -80 +/- 5 kJ/mol and <( Delta H)over bar>(Hf(Ni)) = -137 +/- 8 kJ/mol. These findings are in line w ith phase-diagram data, according to which the Fe-Hf and Ni-Hf systems each contain a few intermetallic compounds. The thermochemical properties of Fe -IVb and Ni-IVb melts are compared. The iron-based melts are characterized by an insignificant increase in heat effects in going from titanium to zirc onium or hafnium. In the Ni-IVb systems, the energy of interatomic interact ions rises in the sequence Ni-Hf --> Ni-Ti --> Ni-Zr.