Nd-Fe-B sintered magnets with low rare earth content fabricated via Dy71.5Fe28.5 grain boundary restructuring

Abstract

Here we report that Nd-Fe-B sintered magnets containing only 12.6–12.9 at.% rare earth elements exhibit maximum energy product (BH)max of 48.0–48.8 MGOe, remanence Br of 1.40–1.41 T, and coercivity Hcj of 12.2–14.5 kOe, which are prepared through introducing eutectic Dy71.5Fe28.5 (at.%) into the near-stoichiometric (Pr,Nd)12.3FebalB6.1 (2:14:1 phase, at.%) magnets via grain boundary restructuring (GBR) approach. The low-melting-point Dy71.5Fe28.5 additive facilitates the liquid phase sintering process to achieve high densification, and generates continuous grain boundary layers that well isolate the main phase grains. Moreover, Dy enrichment at the surface region rather than the center of 2:14:1 grains not only increases the coercivity by enhancing the local magnetocrystalline anisotropy field, but also maintains the remanence. The fact that total rare earth contents of Dy71.5Fe28.5-restructured magnets are much lower than those commercial ones with equivalent magnetic performance (usually 13.5–14.0 at.%) delights the prospective future of GBR approach on fabricating high-performance Nd-Fe-B.