Microstructure modification and coercivity enhancement of Nd-Ce-Fe-B sintered magnets by grain boundary diffusing Nd-Dy-Al alloy

Abstract Grain boundary diffusing process was applied to Nd-Ce-Fe-B sintered magnets using Nd 80- x Dy x Al 20 ( x  = 0, 20, 40, 60, 80 at.%) ribbons. After diffusion treatment at 900 °C for 13 h and annealing at 470 °C for 2 h, the coercivities of processed samples were 12.5, 17.2, 14.9, 15.2 and 14.3 kOe, respectively. The highest coercivity, with a 70% increasement compared to original sample, was achieved using Nd 60 Dy 20 Al 20 with the least Dy content. Microstructural investigations show that the coercivity enhancement of these diffused samples is mainly attributed to the magnetic hardening extensive layers along (Nd,Ce) 2 Fe 14 B grains and weakening magnetic coupling between adjacent grains by continuous intergranular phases. Nd 60 Dy 20 Al 20 is a promising diffusion source for producing high-coercivity Nd-Ce-Fe-B sintered magnets with effective Dy utilization.