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

Abstract

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 (Nd1− x Ce 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, $H_{\mathrm {cj}}= 9.5$ kOe, and $(BH)_{\mathrm {max}} = 42.8$ 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.