Using Al solution calorimetry, enthalpies of formation of Ni3Al in the L12 structure ranging from -41.3 to -42.3kJ/mol were determined at 300 to 1123K. These enthalpies were substantial for an intermetallic compound and exhibited a slight temperature dependence, which was contained within experimental error. This temperature dependence was related to the lack of any transformations of the compound, which remained ordered up to the melting temperature. The measured enthalpies were combined with other thermodynamic data to estimate the excess entropy of formation of Ni3Al. The high degree of ordering in the compound was reflected in the large negative value of the excess entropy, whose absolute value exceeded those for other high melting temperature intermetallic compounds. The full-potential linearized augmented Slater-type orbital method was used to calculate the enthalpies of formation of paramagnetic and ferromagnetic Ni3Al. These enthalpies of formation indicate the compound to be a weak ferromagnet, and they were in good agreement with the calorimetric data.

Enthalpies of Formation of Ni3Al: Experiment versus Theory. Rzyman, K., Moser, Z., Watson, R.E., Weinert, M.: Journal of Phase Equilibria, 1996, 17[3], 173-8