Interdiffusion Behaviors and Microstructure Recombination Mechanisms of Fe2TiO4–CaO and FeTiO3–CaO Systems During Sintering at 1200 °C

Abstract

Vanadium–titanium magnetite (VTM) is an iron ore abundantly available in China. The dominant utilization route is blast furnace smelting; however, Ti in the ore deteriorates sinter strength, making it urgent to clarify Fe-Ti-Ca interactions during sintering. In this work, single-phase FeTiO₃ and Fe₂TiO₄ were synthesized and each paired with CaO to fabricate diffusion couples. The couples were heated at 1200 °C for 30, 60, 90, and 120 min to investigate their interdiffusion behaviors and microstructure recombination mechanisms. The results show that, at 1200 °C, solid-state diffusion—not interfacial reaction—controls mass transfer in both FeTiO₃-CaO and Fe₂TiO₄-CaO systems. Distinct Fe-rich and Ti-rich sublayers appear within the reaction zone, and banded CaTiO₃ forms adjacent to the FeTiO₃/Fe₂TiO₄ matrices. The interdiffusion coefficients were determined to be 4.08 × 10⁻¹⁰ cm²·s⁻¹ and 7.81 × 10⁻¹⁰ cm²·s⁻¹, and the growth of the reaction layer follows a parabolic law, which can be expressed as x² = 2 × 1.562 × 10⁻⁹ t and x² = 2 × 0.8159 × 10⁻⁹ t, respectively. The coefficients of determination exceed 0.90, indicating reliable regression fits.