Coupled Experimental Study and Thermodynamic Modeling of the Al₂O₃–Ti₂O₃–TiO₂ System

Abstract

A complete critical evaluation and re-optimization of phase diagrams and thermodynamic properties of the Al 2 O 3-Ti 2 O 3-TiO 2 system at 1 atm pressure has been performed. Equilibration and quenching experiment in the Al 2 O 3-TiO 2 system in air was also performed to constrain the solubility limit of Al 2 O 3 in TiO 2 rutile solution at high temperatures. The molten oxide phase was described by the Modified Quasichemical Model considering the short-range ordering in molten oxide. While Al 2 TiO 5 and Ti 3 O 5 were treated as separate stoichiometric phases in the previous optimization, they were described in this study, using the Compound Energy Formalism, as part of pseudobrookite solid solution with a miscibility gap based on new experimental data. Corundum and rutile solutions were also described based on their crystal structures. New high temperature phase, Al 6 Ti 2 O 13 , was also considered for the first time. A set of optimized model parameters of all phases was obtained, which reproduces all available and reliable literature data within experimental error limits from 25°C to above the liquidus temperatures under oxygen partial pressures from metallic saturation to 1 atm. The newly optimized database was applied to calculate the inclusion diagram and reoxidation of Al-killed and Ti bearing steels. KEY WORDS: Al 2 O 3-TiO 2-Ti 2 O 3 ; inclusion; pseudobrookite; phase diagram; thermodynamic modeling. * Notations A, G, T are used for Al 3 + , Ti 3 + , and Ti 4 + , respectively. a The Gibbs energies pure liquid AlO1.5 (= 0.5 Al2O3), TiO2 and TiO1.5 (= 0.5 Ti2O3) were taken from and Eriksson and Pelton. 4,5) b The Gibbs energy of pseudobrookite end-members in the Ti-O system were taken from Panda and Jung. 6) c The Gibbs energy of ilmenite end-members in the Ti-O system were taken from Panda et al. 7) β,δ,φ The Gibbs energies of pure solid AlO1.5 (= 0.5 Al2O3), TiO2 and TiO1.5 (= 0.5 Ti2O3) were taken from Eriksson and Pelton. 4,5) ψ The Gibbs energies of pure rutile TiO1.5 (= 0.5 Ti2O3) were taken from Kang et al. 8)

Computational Thermodynamic Calculations: FactSage from CALPHAD Thermodynamic Database to Virtual Process Simulation

“…For example, for low carbon steel at 1550°C in Figure 14(c inclusions can be formed. [62] It is well known that Ti-bearing Al-killed steel is prone to nozzle clogging. Recently, Lee et al [63] experimentally proved that the Ti-bearing Al-killed steel can be reoxidized by CO gas.…”

Distribution of Platinum between the SiO₂–CaO–Al₂O₃–TiO₂ Slag System and Molten Copper

“…Here, ( ) and [ ] represent the X values of the slag and alloy phases, respectively. The oxidation state of Ti in the slag was assumed to be 4 based on previous studies [21][22][23][24].…”

Precipitation of TiS in Al–Ti Simultaneously Deoxidized Steel

“…[3][4][5][6][7] After the deoxidation of aluminum-titanium steel, a variety of nonmetallic inclusions, including oxides, nitrides, and sulfides are formed in the steel. [8,9] Some of these titanium-based inclusions can be used to control the structure of the steel during solidification, such as preventing the growth of austenite grains and assisting in the formation of finer ferrite structures. Therefore, it is essential to investigate the formation mechanism of nonmetallic inclusions in solid steel.…”