Ti Deoxidation Equilibrium in Molten Fe–Cr and Fe–Cr–Ni Alloys at Temperatures between 1823 K and 1923 K

Abstract

Titanium deoxidation equilibria between Ti and O in molten Fe–Cr and Fe–Cr–Ni alloys were investigated at temperatures of 1823 to 1923 K. Titanium oxides equilibrated with molten Fe–Cr and Fe–Cr–Ni alloys have been determined by EBSD (Electron Backscatter Diffraction) pattern analysis using FE-SEM (Field Emission Scanning Electron Microscope). Deoxidation product changes from Ti₂O₃ to Ti₃O₅ with decrease of Ti content in Fe–Cr and Fe–Cr–Ni alloys.
Binary interaction parameters of Redlich–Kister type polynomial between Cr and O was assessed by using the previous experimental result in the Fe–Cr–O system. Experimental result of titanium deoxidation in molten Fe–Cr alloy has been numerically analyzed by the excess Gibbs free energy change of mixing Fe–Cr–Ti–O system with Redlich–Kister type polynomial. Validity of evaluated parameters between Cr–O (Ω_Cr–O) and Cr–Ti (Ω_Cr–Ti) was confirmed by comparison with experimental result for Fe–Cr–Ni alloy.
Binary interaction parameters of Redlich–Kister type polynomial in present work were evaluated as follows,
⁰Ω_Cr–O = −52870−24.10T J/mol (X_O<0.0015, 1823≤T≤1923 K)
¹Ω_Cr–O = −498200+234.7T J/mol (X_O<0.0015, 1823≤T≤1923 K)
⁰Ω_Cr–Ti = 365700−206.3T J/mol (X_Ti<0.003, 1823≤T≤1923 K)
¹Ω_Cr–Ti = 432900−208.8T J/mol (X_Ti<0.003, 1823≤T≤1923 K)