The equilibrium between Ti and O has been investigated in molten Fe–Ti alloy saturated with various kinds of titanium oxides at 1873 K. The present results have been thermodynamically analyzed applying Wagner's formalism as well as Darken's quadratic formalism with the excess Gibbs free energy change of mixing described by Redlich–Kister type polynomial. The equilibrium constants and the interaction parameters of Wagner's formalism were given as follows at 1873 K in the present work.

Ti₂O₃(s)=2Ti+3O (0.5<mass%Ti<6.2)
log K=−10.17, e_O^Ti=−0.34
‘Ti₃O₅’(s)=3Ti+5O (0.0004<mass%Ti<0.36)
log K=−16.86, e_O^Ti=−0.34

The Henry constant of Ti in liquid Fe–Ti alloy was assessed as follows at 1873 K.

γ°_Ti(l)=0.0090

The interaction parameters of Redlich-Kister type polynomial for molten Fe–Ti–O alloy were given by the following values at 1 873 K in the present work.

⁰Ω_Fe–Ti=−73360/J
⁰Ω_Ti–O=−1035900/J

The estimated results based on Wagner's formalism as well as Darken's quadratic formalism polynomials were well agreed with the experimental results which were observed between Ti and O equilibrium contents in molten Fe–Ti alloy.