Feasibility Study of Rapid Solid-State Deoxidation of Titanium Utilizing Rare-Earth Oxyfluoride Formation at Temperatures Approaching 1900 K

Abstract Titanium (Ti) scrap is attracting increased interest as a circular resource, but its widespread use is constrained by oxygen contamination that degrades material properties. Currently, no effective deoxidation method has been established at the industrial scale for recycling Ti scrap. In this study, a novel high-temperature, solid-state deoxidation process is proposed, using rare-earth metals (RE = Y, La, Ce, Nd) as deoxidants and their corresponding fluorides as fluxes to reduce oxygen potential in the system through the formation of rare-earth oxyfluorides (REOF). Thermodynamic calculations demonstrate that several chemical equilibria such as Y/YOF/YF 3 can reduce the oxygen concentrations in solid Ti to 200 mass ppm or less at 1900 K, well below the 500 mass ppm threshold required for industrial applications. Kinetic modeling for oxygen diffusion in solid Ti indicates that the oxygen concentration of a 40 mm-diameter Ti sphere can be lowered from 4200 to below 600 mass ppm within 6 hours at 1900 K. This deoxidation rate is over 5000 times higher than that achieved at conventional processing temperatures around 1300 K, demonstrating the potential of this high-temperature approach to produce low-oxygen Ti feedstock suitable for remelting and industrial use.