Electrochemical Synthesis Quaternary Mg−Li−Al−Pr Alloy with and without Whisker on Magnesium Cathode in LiCl−KCl−PrCl3−AlCl3 Melts

Abstract

The electrochemical behavior of Pr(III) was firstly studied by different electrochemical measurements, and the Mg−Li−Al−Pr alloys with different alloy phases were prepared by galvanostatic electrolysis. Meanwhile, the electrochemical behavior of Mg(II) was also investigated by cyclic voltammetry and chronopotentiometry, and the diffusion coefficient of Mg(II) in LiCl–KCl melts was finally determined by chronopotentiometry. The results from different electrochemical measurements which were measured in LiCl−KCl−MgCl2−AlCl3−PrCl3 melts exhibited that two kinds of Al−Pr intermetallic compounds (Al2Pr and Al3Pr) and one kind of Mg−Pr intermetallic compound (Mg12Pr) were formed. Chronopotentiometry illustrated that the co−deposition of Mg(II), Li(I), Al(III) and Pr(III) ions will be realized when the current intensity is more than −200 mA (S = 0.322 cm2). Quaternary Mg−Li−Al−Pr alloys with and without whiskers were prepared on Mg cathodes by galvanostatic electrolysis in LiCl−KCl−AlCl3−PrCl3 melts. The deposits were finally analyzed by XRD, SEM and TEM with electron diffraction test. The result from the SEM analysis exhibited that the element aluminum existed in the form of Al−Pr intermetallic compound whiskers in the Mg−Li−Al−Pr alloy, which was obtained by galvanostatic electrolysis on liquid magnesium electrode. The micro hardness and corrosion resistance of Mg−Li−Al−Pr alloys were enhanced significantly with the assistance of Al−Pr intermetallic compound whiskers.