Fabrication of Mg–Pr and Mg–Li–Pr alloys by electrochemical co-reduction from their molten chlorides

Abstract

This work presents the electrochemical deposition of Mg–Pr and Mg–Li–Pr alloys on tungsten electrodes in molten LiCl–KCl–MgCl2–PrCl3 system. The electrochemical behavior of Mg(II), Pr(III), and Li(I) ions and alloy formation process in the melts were investigated by cyclic voltammetry (CV) and open circuit chronopotentiometry (OCP). Spherical bulk alloys were obtained by potentiostatic and galvanostatic electrolysis at −1.85V for 3h and −6.00Acm−2 for 2h, respectively. Pr and Li contents in the alloys were regulated by changing the concentration of PrCl3 and MgCl2 in the melts. The proportion of Pr was controlled from 9.73 to 19.93wt.% in Mg–Pr alloys and the ratio of Li changed from 0.10 to 37.27wt.% in Mg–Li–Pr alloys. X-ray diffraction (XRD) indicated that Mg–Pr alloys were solely comprised of α-Mg and Mg12Pr phases. However, in Mg–Li–Pr alloys, the phases were transformed from Mg12Pr to Mg3Pr, accompanied by the transition of matrix (from α-Mg to β-Li). The microstructure and micro-zone chemical analysis of Mg–Pr and Mg–Li–Pr alloys were characterized by scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS).