Thermodynamics of the Al3Ni phase and revision of the Al–Ni system

The heat capacity of the Al3Ni phase had been measured for the first time, by means of relaxation method over the low temperature range 2–323 K and by measuring heat content increments using drop calorimetry over the higher temperature range of 583–1073 K. The Debye function was employed to fit the low-temperature heat capacities, and from the function, the absolute entropy was evaluated, S298∘=25.4 J/mol-atoms K. A three-term polynomial representation, a + b·T + c·T−2, was used for describing heat capacity above 298.15 K. The Gibbs energy function of the Al3Ni phase was derived with a fixed reference state by incorporating the polynomial expression of the heat capacity, the recently reported enthalpy of formation and the related phase equilibria in the Al–Ni system. A revised thermodynamic description of the entire Al–Ni system together with the calculated phase diagram is also presented.