2008 Volume 48 Issue 6 Pages 729-738
The equilibrium relation between Ti and O in liquid Fe has been measured only at 1873 K on the condition of various kinds of titanium oxides saturation in our previous paper. The present work deals with the equilibrium between Ti and O in liquid Fe saturated with ‘Ti3O5’ and Ti2O3 at 1823 K and 1923 K for full understanding temperature dependence. Also, equilibrium phase changes of titanium oxides with various Ti contents in molten Fe have been identified as the equilibrium titanium oxides with electron backscatter diffraction (EBSD) pattern analysis technique. The present results have been thermodynamically evaluated combining with previous results on the various thermodynamic values as a function of temperature.
The equilibrium constants and the interaction parameters of Wagner's formalism were given as a function of temperature in the present work as follows.
Ti2O3(s) = 2Ti+3O
log KTi2O3 = −42940/T+12.94, (1823 K<T<1923 K) (−10.61, 0.28<mass%Ti<4.89, at 1823 K
−9.99, 0.40<mass%Ti<6.22, at 1873 K
−9.39, 0.52<mass%Ti<2.79, at 1923 K)
eOTi = −701/T+0.0344, (1823 K<T<1923 K)
‘Ti3O5’(s) = 3Ti+5O
log K‘Ti3O5’ = −68280/T+19.95, (1823 K<T<1923 K) (−17.50, 0.01<mass%Ti<0.28, at 1823 K
−16.52, 0.006<mass%Ti<0.40, at 1873 K
−15.56, 0.0045<mass%Ti<0.52, at 1923 K)
eOTi = −701/T+0.0344, (1823 K<T<1923 K)
The Henry constant of Ti in liquid Fe was estimated as a function of temperature.
ln γ°Ti(l) = −20890/T+6.228, (1823 K<T<1923 K)
The self-interaction parameter of Ti in liquid Fe was obtained as a function of temperature.
eTiTi = 212/T−0.0640, (1823 K<T<1923 K)
The interaction parameters of Redlich–Kister type polynomial for molten Fe–Ti–O alloy were given as the following values in the present work.
0ΩFe–Ti = −173600+51.76T/J, (1823 K<T<1923 K)
0ΩTi–O = −1189000+82.00T/J, (1823 K<T<1923 K)
The estimated results based on Wagner's formalism as well as Darken's quadratic formalism with Redlich–Kister type polynomials agreed well with the experimental results at 1823 to 1923 K.
