Experimental investigation of diffusion behavior between molten Mg and Nd–Fe–B magnets

Highlights: • Extraction behaviors of Nd in Nd–Fe–B magnets by liquid Mg were evaluated. • The diffusion layer grew with increasing melting temperature and casting time. • The diffusion coefficients for Nd into liquid Mg were calculated. -- Abstract: This study presents the experimental results of neodymium (Nd) extraction from the Nd–Fe–B magnetic alloy by liquid magnesium (Mg). A sample of Nd–Fe–B alloy was placed in an Fe crucible with pure Mg under an Ar atmosphere and melted by induction heating. In order to identify the reaction mechanism, the effects of melting temperature (993–1073 K) and holding time (2–120 min) on the extraction ability were investigated. The diffusion behavior was analyzed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) and the constituent phases were characterized by X-ray diffraction (XRD). It was found that Nd from the Nd–Fe–B alloy diffused readily into liquid Mg. The reaction rate was dependent both on temperature and time. This study demonstrates that liquid metal extraction of Nd could be a viable and inexpensive method for recovery of the expensive rare earth element Nd using Mg castings