In-Situ X-ray Diffraction/Fluorescence Analysis of Dy–Cu Electrochemical Alloying and Dealloying in Molten LiCl–KCl–DyCl3

Abstract

Recycling spent Nd magnets is essential for maintaining a stable supply of rare earth (RE) elements prompting the development of a one-step recycling process using molten salt and alloy diaphragms. In this study, to investigate the mechanism of rapid alloy formation, an in-situ X-ray diffraction/fluorescence analysis of Dy–Cu electrochemical alloying and dealloying in molten LiCl–KCl–DyCl3 was performed. During the electrolysis, a diffraction peak corresponding to Cu was observed. In addition, X-ray fluorescence peaks of Dy were observed throughout the process. The area of the Dy X-ray fluorescence peak increased as the alloying progressed but remained relatively constant during the dealloying process. Compared with Dy–Ni alloying/dealloying, the areas of the fluorescence peaks were smaller. The results suggest a slower alloy formation rate with Cu than with Ni. Cross-sectional images show that the alloy formation rate is lower for Cu, which can be attributed to a larger crystal mismatch between the substrate and alloyed layer.