Towards the Improvement of the Short-Loop Recycling of Dy-Rich Nd-Fe-B Permanent Magnets: Experimental and Numerical Approaches
Résumé
The method of short-loop recycling of Nd–Fe–B magnets is implemented, withend-of-life (EoL) magnets used as a source of heavy rare earth (HRE). Partiallyrecycled magnets are fabricated by co-sintering HRE-free powders obtained fromstrip casted alloys, blended with HRE-rich powders obtained from EoL magnets.The impact of several process parameters (blending ratio, sintering cycle, andHRE-rich recycled particle sizes) on the microstructure and magnetic propertiesis discussed. A coercivity gain up to 160 kA m1 wt%1 of Dy with respect to theHRE-free magnets is reported, even though impurities are incorporated.Microstructural characterizations show a heterogeneous Dy localization in core–shell/anticore–shell structures, and thus a nonoptimal use of HRE. The exper-imental results are compared with finite element simulations of the Dy diffusiontransport performed using existing data of bulk Dy diffusion coefficients. Thesimulation model consists of a network of square grains separated by a liquidphase, whose fraction is based on the ternary Nd–Fe–B phase diagram. Resultsshow similarities with the observed microstructures, and point to the interest ofreducing the Dy-rich particle size with respect to the main powder. This studyprovides new insights into the Dy transport mechanisms at stake in an efficientshort-loop recycling of HRE.RESEARCH ARTICLEwww.aem-journal.comAdv. Eng. Mater. 2024, 26, 2400234 2400234 (1 of 13) © 2024 The Authors. Advanced Engineering Materials published by Wiley-VCH GmbH
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