Balancing the microstructure and chemical heterogeneity of multi-main-phase Nd-Ce-La-Fe-B sintered magnets by tailoring the liquid-phase-sintering

Retaining chemical heterogeneity of 2:14:1 grains and forming continuous grain boundaries are two critical contributions to the strong magnetism in multi-main-phase (MMP) magnets. However, the ideal grain boundary microstructure is usually achieved at the expense of weakening the chemical heterogeneity, which poses a big challenge. Here we report a versatile strategy to balance the chemical heterogeneity and microstructure of MMP Nd-Ce-La-Fe-B magnets through tailoring liquid-phase-sintering. At optimum 1040 degrees C sintering, MMP magnet with 27 wt% Ce-La substitution level exhibits an equivalent weight-bearing capacity to 40MGOe commercial Nd-Fe-B, which is attributed to the joint contributions from retained chemical heterogeneity, essential densification, homogeneous grain size distribution and continuous intergranular phase network with ordered Ia (3) over bar structure. When shifting sintering temperature T-s towards the higher or lower range, the deteriorated magnetic properties are dominated by distinct restraints. With Ts above 1040 degrees C, the decreased coercivity is mainly restrained by the negative role of gradual chemical homogenization and abnormal grain growth, as verified by experimental and simulated results. However, with Ts below 1040 degrees C, the unsatisfactory magnetic performance mainly roots in insufficient densification and discontinuous grain boundary. These advances may deepen our understanding on designing high-performance MMP magnets with balanced contributions from modified microstructure and retained chemical heterogeneity. (c) 2019 The Authors. Published by Elsevier Ltd.