Microstructures and magnetic properties of PrNd-free (Ce, RE)-Fe-B (RE = Y, La) sintered magnets

The phase constitutions and microstructure characteristics of PrNd-free (Ce, RE)-Fe-B (RE = Y, La) sintered magnets were investigated, and the effects of Y and La substitution on the microstructures and magnetic prop-erties of Ce-based magnets were discussed. It indicated that the Ce-Fe-B strip casting (SC) alloy has an inho-mogeneous lamellar crystalline structure, the uniformity of lamellar crystalline was improved by Y substitution, and an obvious refined crystalline structure has been obtained in the Y and La co-substituted SC alloy. The experimental Ce-based SC alloys were mainly composed of RE2Fe14B and REFe2 phases. Some "small islands" existing in REFe2 regions were identified as intermediate products of the peritectic reaction. It inferred that a trace amount of alpha-Fe existed in all the Ce-based SC alloys. The Ce-Fe-B sintered magnet has a large-grain microstructure, and several main-phase grains often directly contact without the isolation of RE-rich phases. Therefore, the intrinsic coercivity of the Ce-Fe-B sintered magnet was very low, equal to that of a soft magnetic material. The grains were obviously refined by Y and La co-substitution, and the magnetic properties of the corresponding magnet have increased remarkably. A Br of 8.31 kG, Hcj of 0.92 kOe, and (BH)max of 5.30 MGOe were obtained in the PrNd-free (Ce, Y, La)-Fe-B sintered magnet.