Microstructure and magnetic properties of (Nd,Pr,Ce)-Fe-B magnets

To develop low-cost sintered Nd-Fe-B magnets, 30% Ce was used to substitute for Nd and Pr in magnets with the nominal compositional (Nd_0.75Pr_0.25)_32.69Fe_66.25B_1.06. The microstructure and magnetic properties of the magnets were studied during the processes of sintering and tempering. It is found that the magnetic properties of the orientated compacts decrease with the sintering temperature increasing from 1030 to 1080 ℃, and the magnets sintered at 1030 ℃ for 2 h exhibit the best magnetic properties. Compared with the non-substituted magnets, the Ce-substituted magnets show higher magnetic properties. The phase composition and grain size do not show obvious change along boundary structure by one-order tempering, and the magnetic properties of the magnets keep the same, or decrease slightly. By two-order tempering, the eoercivity of the magnets is greatly improved by optimization of boundary microstructure, with more clear and straight boundaries. The remanence, coercivity, and maximum energy product of the Ce-substituted magnets are slightly lower than those of the non-substituted magnets.