Electrolytic preparation of Mg-Al-La alloys in KCl-MgCl2-AlF3 molten salts

Abstract

A KCl-MgCl2-AlF3 ternary system containing La2O3 was investigated for the preparation of Mg-Al-La master alloy by electrodeposition technique. The cyclic voltammetry and chronopotentiometry indicated that the co-reduction of Mg, Al and La occurs at cathode-current densities more negative than −0.29A·cm−2. Lanthanum under-potential deposited on pre-reduced Al and it formed Al-La alloy. Inductively coupled plasma-optical emission spectroscopy (ICP-OES) and X-ray diffraction (XRD) analyses were used to consider the contents of components in the alloy, the supernatant composition of molten salt after dissolution of La2O3 and the composition of the alloy, respectively. The galvanostatic electrolysis results showed that the optimum electrolysis conditions were the electrolytic temperature of 800℃, the cathode-current density of 6.92A·cm−2, and the electrolysis time of 60min. The XRD and SEM analysis results showed that the main phases of the obtained alloy sample were α-Mg, α-Mg+β-Al12Mg17 and α-Mg+Al11La3. The content of magnesium in the Mg-Al-La alloy reach with the increase of the cathode-current density.Inductively coupled plasma-optical emission spectroscopy (ICP-OES) analyses of Mg-Al-La alloy samples showed that aluminum and Lanthanum contents of Mg-Al-La alloys could be controlled under the several cathode-current density.