The Study on Grain-Boundary Microstructure of Sintered (Ce, Nd)–Fe–B Magnets

In this paper, the structure and magnetic properties of the (Ce, Nd)-Fe-B magnets without Dy and Tb substitution have been investigated. The purpose of the investigation is to develop the applicable Ce-Fe-B magnets with Ce content over 50 wt.%. Sintered (Ce, Nd)-Fe-B magnets with the nominal composition of (Nd_1-xCe_x)₃₀(Fe, TM)_balB₁ (x = 0-0.75) in wt.% were fabricated by advanced powder metallurgy processes. The effects of Ce substitution on the microstructure and magnetic properties of the (Ce, Nd)-Fe-B magnets were discussed. It was found that the (Ce, Nd)-rich boundary phase with lower melting point is helpful to obtain improved boundary microstructures and refined grain magnets. Good magnetic properties of Br = 13.5 kG, H_cj = 9.5 kOe, and (BH)_max = 42.8 MGOe were obtained in the Dy-free (Ce, Nd)-Fe-B magnets with 30 wt.% Ce substitution. A higher coercivity (>10 kOe) has been achieved in the Ce-Fe-B type magnets by the modifications of alloy compositions and the optimization of preparation conditions, in which the proportion of Nd and/or Pr is lower than 35 wt.% of the total rare-earth content.