Electrochemical reduction of Al(III) and Si(IV) in the NaF-AlF3-Al2O3-SiO2 molten salt system and preparation of homogeneous Al-Si alloys by molten salt electrolysis

The segregation of aluminum-silicon alloys directly impacts the mechanical and chemical properties of the alloys, Therefore, homogenization of alloys is of great significance for alloys. This study initially investigated the electrochemical behavior of aluminum (III) and silicon (IV) during the preparation of aluminum-silicon (Al-Si) alloys in NaF-AlF 3 -Al 2 O 3 -SiO 2 molten salts through cyclic voltammetry and steady-state polarization. The results revealed that Al 2 O 3 underwent one-step reduction to Al, whereas SiO 2 underwent a two-step reduction process to Si. In addition, electrolysis experiments were carried out in a NaF-AlF 3 -Al 2 O 3 -SiO 2 -5wt%CaF 2 -1wt%MgF 2 -2wt%LiF molten salt system with molecular ratio of 2.4. These experiments involved variations in current density, electrolysis time, Al 2 O 3 and SiO 2 additions. It is worth noting that under the conditions of current density of 0.7 A/cm 2 , electrolysis time of 2 h, and silica addition of 2 %, the reduction rate of silicon reached a maximum value of 72.57 %, at which time the silicon in the aluminum-silicon alloys showed a dendritic structure, which was uniformly distributed throughout the entire alloy, and the segregation of the alloy was effectively avoided.