There is an ever-growing
demand for the use of aluminum-lithium alloys in the aerospace industry,
because of their lightweight and improved modulus. Presently these alloys
are produced by the melting and casting method involving the use of pure
metallic lithium which is added to the molten aluminum. The production of
Al-Li alloys by mixing the pure metal is an energy intensive and expensive
process. Considering the relatively high prices of high purity lithium
metal, a new process is investigated in the present research to prepare
lithium by in situ electrolysis of lithium compounds to Al-Li alloys in
To study the viability of a process for obtaining a metal from its
compound, it is necessary to obtain sufficient information on the
solubility of the oxide in fluoride melts. Two lithium compounds, Li2O
and Li2CO3, are tried in the present investigation.
Their solubilities in LiF-CaF2 melts at various temperatures
and also the liquidus temperature of the eutectic mixtures are measured.
Using the solubility data, other thermodynamic data such as integral molar
enthalpy, entropy, and Gibbs energy of formation have been calculated.
Cathodic current efficiency and anodic overvoltage are the critical
parameters to evaluate the electrolysis process efficiency. Anodic
overvoltage measurements on graphite anode during electrolysis of Li2O
in LiF-CaF2 were made using steady state current voltage method
and limiting current density in the melt is determined. Work is in
progress to evaluate other parameters and to compare the process
efficiency obtained with different lithium compounds.