Recycling of Magnesium Alloys: Chemical Equilibria between Magnesium-Lithium-Based Melts and Salt Melts

摘要

Magnesium-lithium alloys have been equilibrated with chloride melts at 700 deg C in iron crucibles. After quenching, the compositions of the metal and salt phases were determined by chemical analyses. The obtained data were evaluated according to thermodynamic principles. The following reactions were investigated: MgCl_2+2Li=2LiCl+Mg(Reaction [1]), CaCl_2+2Li=2LiCl+Ca (Reaction [2]), and BaCl_2+2Li=2LiCl+Ba (Reaction [1]), CaCl_2+2Li=2LiCl+Ca (Reaction [2]), and BaCl_2+2Li=2LiCl+Ba(Reaction [3]). The equilibrium of Reaction [1] is much on the right side of the reaction equation. If calcium chloride or barium chloride are added to the salt mixture (to increase the density), these chlorides are partially reduced, leading to pickup of calcium or barium, respectively, by the metal phase. Reaction [1] can be utilized in two different recycling schemes. With a magnesium chloride free lithium chloride-potassium chloride mixture, remelting of magnesium-lithium alloys is possible without loss of lithium to the slag. On the other hand, the lithium can be separated from the magnesium by conversion to lithium chloride using a magnesium chloride rich slag.