Investigation on the grain boundary diffusion of Dy2O3 film prepared by electrophoretic deposition for sintered Nd-Fe-B magnets

Abstract

Based on the diffusion source of Dy2O3 film prepared by electrophoretic deposition (EPD), grain boundary diffusion (GBD) is performed to improve properties of sintered Nd-Fe-B magnets. Effects of EPD and GBD processes on microstructure and magnetic properties are investigated in details. The studied results show that 30 s of EPD time is the most suitable for the preparation of diffusion source, and the optimal magnetic properties with Hci of 934 kA/m, Br of 1.41 T and (BH)max of 349 kJ/m3 can be achieved under GBD condition of 800 °C/6 h followed by 500 °C/1 h, enhancing by 27.6%, 0.7% and 13.7%, respectively, comparing to those of as-prepared magnet. The formation of (Nd, Dy)2Fe14B shell surrounding Nd2Fe14B core and improved distribution and structure of rare earth-rich (RE-rich) phase jointly contribute to the improvement of coercivity. Moreover, Thermal stability (temperature coefficient of remanence and coercivity) is improved considerably. Dense Dy2O3 film and formed filamentous substance covering the surface together promote the improvement of corrosion resistance.