Synthesis of Al–Sc Binary Alloys via Aluminothermic Reduction of Sc2O3 in NaF–AlF3–LiF Flux Systems

The rising demand for Al–Sc alloys in advanced manufacturing sectors underscores the need for more efficient and cost-effective production methods. Here, we developed a novel molten salt system based on Na₃AlF₆-LiF (with a NaF/AlF₃ molar ratio of 2.2) and present an innovative three-stage countercurrent process that, for the first time, achieves the direct one-step aluminothermic reduction of Sc₂O₃. The first-stage reaction yields an Al–Sc alloy with 1.82 wt pct Sc, while the complete three-stage process produces a final alloy containing 1.33 wt pct Sc with remarkable 85.72 pct Sc₂O₃ utilization rate. By systematically elucidating the phase evolution and compositional transformations within the molten salt system during the reaction, and through the optimization of key parameters—including the cryolite-to-Sc₂O₃ mass ratio (5.2), LiF addition (8 wt pct), and reaction conditions (950 °C, 1.5 hours)—we significantly enhance both the reaction kinetics and the alloy quality. Compared to conventional processes, this streamlined method substantially reduces energy consumption and environmental impact, offering a scalable and sustainable pathway for the industrial production of Al–Sc alloys.