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Electrochemical formation of Al-Sc alloy in molten salt

2019
Polat, Çağlar
Al-Sc alloys have better mechanical properties in comparison to commercial aluminum alloys. The aim was to produce Al-Sc alloys containing at least 2wt % scandium by electrochemical reduction of the byproducts such as ScF3 or the alternative compounds obtained from hydrometallurgical processing of low grade lateritic nickel in this thesis. Electrochemical production of Al-Sc alloy in pure molten CaCl2 and CaCl2-NaCl mixtures was studied for this purpose. The graphite-liquid aluminum-CaCl2 or CaCl2-NaCl interaction, the effect of voltage and duration of the electrolysis on Sc recovery rate, the coalescence behavior of the electrolytic Al-Sc alloy in molten CaCl2 and CaCl2-NaCl mixtures, the effect of CaO left from the dehydration process on the purity of Al-Sc alloy and the effect of NaCl addition into the electrolyte were investigated. In addition, solubility behavior of ScF3 in pure molten CaCl2 and CaCl2-NaCl mixtures and utilization of different cathode materials and ceramic membranes were examined. According to the results of the optical microscopy, SEM-EDS and XRD analyses, Al-Sc alloys were produced successfully by electrochemical reduction of domestic scandium bearing powder containing ScF3, NaScF4 and Na3ScF6 phases. Alloying in-situ with liquid aluminum in both molten CaCl2 and CaCl2-NaCl salt mixtures with molten salt electrolysis method was possible.