Phase equilibria of CaO-Al2O3-CaO.TiO2 system at 1500 °C in hydrogen atmosphere

The phase diagram of CaO-Al2O3-TiOx system is of great importance in guiding the design of metallurgical slag systems for Al-Ti alloy steel, controlling Ti-bearing inclusions in molten steel, and regulating the mineral phase of vanadium-titanium magnetite. In the present work, the high temperature equilibration-quench technique was adopted, and the types and compositions of equilibrium phases were identified by Electron Probe Micro Analysis (EPMA) and X-ray diffraction (XRD). The isothermal section of CaO-Al2O3-CaO.TiO2 system at 1500 degrees C in H-2 atmosphere was constructed for the first time. There are 7 three-phase fields, 10 two-phase fields, and a single liquid phase field. On this basis, according to the theoretical analysis of the crystal structure, the formation energy analysis based on first-principles calculations, and the related theories of defect chemistry, the formation mechanisms of CaTiO3 and Ca3Ti2O7 solid solution with were determined, respectively. Additionally, the experimental phase diagram was utilized to discuss the dissolution type and the equilibrium solubility of typical inclusions (Al2O3, Ti3O5, and CaO.TiO2) in Al-Ti alloy steel.