Enhancing the Properties of Spark Plasma Sintered Nanocrystalline NdFeB Magnets by the Addition of Cu-Zn Alloy and Dy2O3 Powders

Nanocrystalline NdFeB bulk magnets were synthesized by doping non-rare earth CuxZn100-x (x = 0, 10, and 60 wt.%) alloy powders and low-cost Dy2O3 powders into melt-spun Nd10.15Pr1.86Fe80.41Al1.67B5.91 powders using spark plasma sintering (SPS). Their microstructure and magnetic properties were systematically studied. The results indicate that in the magnets doped with 1.0 wt.% Cu10Zn90 powders, Cu or Zn is evenly partitioned in irregular particle interfaces, which can improve the densification during SPS due to the "connection" effect. Zn or Dy2O3 plays an important role in suppressing grain coarsening of the Nd2Fe14B phase during SPS. Doping with 0.5 wt.% Zn, 0.5 wt.% Cu10Zn90 or 0.1 wt.% Cu60Zn40 powders can effectively improve the magnetic properties of the final products, and their intrinsic coercivities (H-j(c)) are about 11.3%, 15.6%, 11.7% higher, respectively, than that of the additive-free magnet. Meanwhile, the SPS magnets doped with 0.5 wt.% Zn or 0.5 wt.% Cu10Zn90 powders show high H-j(c) values with slight increases in both remanent magnetic polarization J(r) and maximum energy product (BH)(max). The magnets doped with both 0.1 wt.% Cu60Zn40 and 1.0 wt.% Dy2O3 powders exhibit the highest H-j(c) of 1630 kA/m.