Determination of the thermodynamic properties of Ni-Ti, Ni-Al, and Ti-Al, and nickel-rich Ni-Al-Ti melts based on the atom and molecule coexistence theory.

The thermodynamic properties of the full composition range of liquid Ni-Ti, Ni-Al, and Ti-Al alloys were determined using the atom and molecule coexistence theory (AMCT), which is an established thermodynamic model that was used to calculate the mass action concentration (activity) of the structural units in the abovementioned three alloy systems. The temperature dependence of the activity coefficients γ i θ of Ti and Al dissolved in molten nickel to form dilute solutions (0 ≤ x i ≤ 0.01) relative to pure liquid were estimated from the calculated activity coefficients of Ti and Al at different temperatures. The standard Gibbs free energy changes Δ sol G m , i θ of dissolving Ti and Al in nickel and the enthalpies of mixing Δ mix H m, i of liquid Ni-Ti, Ni-Al, and Ti-Al were also obtained. The results indicated that the determined thermodynamic properties, such as the Δ sol G m , i θ , and Δ mix H m, i of the liquid binary alloys reasonably agreed with the experimental data previously reported in the literatures. Thermodynamic properties were predicted for three important subsystems, which included the Ni-Ti, Ni-Al, and Ti-Al alloys, and therefore, the activity a i and Δ mix H m, Ni‐Al‐Ti of the nickel-rich liquid Ni-Al-Ti ternary alloys were also obtained at 1873 K. Furthermore, the values calculated using the classical geometric models, including the Toop, Kohler, and Muggianu models, were compared with those determined by the GSM in this study. • Atoms and molecules coexist in the liquid Ni-Al-Ti ternary alloys. • Thermodynamic properties of liquid Ni-Ti, Ni-Al, Ti-Al binary alloys • The enthalpies of mixing of nickel-rich liquid Ni-Al-Ti ternary alloys at 1873 K. [ABSTRACT FROM AUTHOR]