Thermodynamic Properties of Ni-Ti-Si Ternary Alloy and Calculation of Amorphous Formation Range

The formation enthalpy ΔH, excess entropy S^E, excess Gibbs free energy G^E, and activity of each constituent element of Ni-Ti-Si ternary alloy at 1 273 K is calculated based on Chou model, and the formation enthalpies of 8 intermetallic compounds of the Ni-Ti-Si ternary alloy are calculated. The amorphous formation range of Ni-Ti-Si ternary alloy at 1 273 K is predicted based on Toop model. The calculated results show that when x_Ni=0.39, x_Ti=0.25, and x_Si= 0.36, the Ni-Ti-Si ternary alloy has the minimum ΔH, S^E and G^E, and ΔH_min=-56.25 kJ/mol, S^E_min=-6.38 J/mol, and G^E_min=-48.14 kJ/mol. Of the 8 intermetallic compounds, the ΔH of the intermetallic compound τ₁ is the most negative, indicating that its phase stability is the highest. It is the first to precipitate, τ₂, τ₆, τ₇ and τ₈ are the next, and τ₃, τ₄ and τ₅ are the last. Ni-Ti-Si ternary system has a very large negative deviation between the activity values of each constituent element and the ideal melt. Amorphous can be formed in the Ni-Ti-Si ternary alloy, and the amorphous formation range is very large, mainly in the composition range of x_Ti=20%~80% and x_Ni=15%~90%. The calculated range of intermetallic compounds and amorphous formation range of Ni-Ti-Si ternary alloy are in good agreement with the experimental results.