Novel Electrolytic Process for the Direct Production of Al–Mg Alloy from MgO Using an Al Cathode

Abstract A novel molten salt electrolysis process using an aluminum (Al) cathode was developed to directly produce Al–magnesium (Mg) alloys from magnesium oxide (MgO). The effects of the temperature of electrolysis, concentration of Mg in the Al–Mg alloy, and cathodic current density on the current efficiency were investigated. The electrolysis was conducted via chronopotentiometry at 1053–1173 K in a 33 mol% magnesium fluoride (MgF 2 )–47 mol% lithium fluoride (LiF)–calcium fluoride (CaF 2 ) molten salt using an Al cathode and a carbon (C) anode under an argon (Ar) atmosphere, with the cathodic current densities ranging from 0.159 A·cm –2 to 0.477 A·cm –2 for 160–480 min. During electrolysis, Al–Mg alloys were produced through the electrochemical reduction of MgO at an average cell voltage of 1.95–2.33 V. Under certain conditions, a current efficiency of 87.1–97.9% was achieved with 13.65–23.65 mass% Mg alloys, which consisted of Al 3 Mg 2 and Al (Mg) phases. Therefore, the novel electrolytic process using an Al cathode demonstrates the feasibility of the direct production of Al–Mg alloys from MgO.