Influence of introducing TiO2 on densification and thermal shock resistance of Al2O3-MgO-CaO-Y2O3 materials

Abstract

To develop a novel refractory system for cleaner steelmaking and alloy smelting, Al₂O₃-MgO-CaO-Y₂O₃ materials were successfully synthesized via the solid-phase method, utilizing Al₂O₃-MgO-CaO as well as Y₂O₃ as the primary raw materials, with TiO₂ serving as an additive. The impact of TiO₂ on the sintering behavior, mechanical properties, and thermal shock resistance of the material was further investigated to elucidate its influence mechanism. The findings reveal that the addition of TiO₂ led to an increase in the volume shrinkage ratio of the samples from 23.40% to 30.14%, a decrease in bulk density from 3.11 g·cm⁻³ to 2.85 g·cm⁻³, and an increase in apparent porosity from 9.52% to 18.00%. Furthermore, the cold compressive strength of the samples decreased from 108.6 MPa to 54.64 MPa, and the residual strength ratio after three cycles of thermal shock decreased from 78.10% to 66.14%. The internal structure of the material primarily consists of MgAl₂O₄, Al₅Y₃O₁₂, and CaAl₂O₄ phases, formed at different reaction stages (initial, intermediate, and final stages). The formation conditions of these crystal phases significantly influence the microstructure and properties of the material. Upon the addition of 6 wt% TiO₂, numerous Al₂TiO₅ and Mg₂TiO₄ precipitate from the continuous liquid phase during cooling, along with partially unreacted Al₂O₃. These grains exhibit relatively small size and high content, leading to an increase in energetically mismatched grain boundaries and interfaces among the internal grains, thereby augmenting the overall structural inhomogeneity of the material. Consequently, this diminishes the mechanical property and thermal shock resistance of the materials.