Synergistically tailoring the microstructure and chemical heterogeneity of nanocrystalline multi-main-phase Nd–Ce–Fe–B magnet: Critical role in magnetic performance

The microstructure and chemical heterogeneity play critical roles in the magnetic performance of nanocrystalline multi-main-phase (MMP) Nd–Ce–Fe–B magnets. In this work, we report a strategy to synergistically tailor the microstructure and chemical heterogeneity of MMP magnet through optimizing sintering temperature (Ts). An optimum Ts of 700 °C has been obtained for nanocrystalline MMP Nd–Ce–Fe–B magnets. When sintered at Ts = 700 °C, the nanocrystalline MMP magnet exhibits the maximum intrinsic coercivity Hcj, the preferable remanence Br, and the resultant optimum maximum energy product (BH)max, which is attributed mainly to the appreciable density, controlled grain size, and better chemical heterogeneity. Comparably, lower or higher Ts leads to the inferior magnetic properties. At lower Ts below 700 °C, the poor magnetic properties are mainly due to the insufficient densification. However, at higher Ts above 700 °C, the decreased Hcj originates mainly from the excessive grain growth and gradual chemical homogenization. The above findings deepen our understanding on the relationship among the microstructure, chemical heterogeneity, and Ts, concurrently providing an effective approach for fabricating low-cost high-performance nanocrystalline MMP Nd–Ce–Fe–B magnets. •Microstructure and chemical heterogeneity of nanocrystalline MMP Nd–Ce–Fe–B magnet are synergistically tailored.•Hcj, Br, and (BH)max are simultaneously enhanced at optimum Ts of 700 °C.•Dependences of microstructure and composition on Ts are revealed, and an evolution model is proposed.•Mechanisms underlying changes in magnetic properties with Ts are systematically analyzed.