To restrict grain growth in coarse grain regions caused by the diffusion of Nd-Cu eutectic alloys,the Nb element was introduced into the precursor alloy to regulate the microstructure of melt-spun powder and die-upset magnets.The magnetic properties and thermal stability of die-upset magnets were appreciably improved through the addition of Nb.For the Nb-doped diffusion die-upset magnet,the grains inside the ribbons were refined and the coarse non-oriented surface crystallite got suppressed on the interface of ribbons during the hot-deformation process to form the anisotropic magnet.Moreover,Nd gathers at the intergranular phases,which is considered to enforce domain wall pinning force.The Nb-modified microstructure is advantageous to thermal stability and coercivity enhancement.High-resolution trans-mission electron microscopy images revealed that the Nb element gathered on the grain boundary and triple grain boundary to form c-Nb and h-NbFeB to hinder the grain growth during the hot-deformation process,which led to direct enhancement in the coercivity.Furthermore,the c-Nb and h-NbFeB are non-magnetic phases that strengthened the magnetic isolation.However,the h-NbFeB precipitated from the hard magnetic phase and formed crystal defects which led to remanence deterioration.

School of Marine Engineering Equipment,Zhejiang Ocean University,Zhoushan 316022,China;CAS Key Laboratory of Magnetic Materials and Devices,Ningbo Institute of Material Technology and Engineering,Chinese Academy of Sciences,Ningbo 315201,China;Grirem Advanced Materials Co.,Ltd.,Beijing 100049,China

[1]Tingting Song;Xin Li;Xu Tang;Wenzong Yin;Yang Luo;Dunbo Yu;Wenlong Yan;Jinyun Ju;Renjie Chen;Aru Yan-.Effect of Nb doping on microstructure and magnetic properties of hot-deformed Nd-Fe-B magnets with Nd-Cu eutectic diffusion)[J].材料科学技术（英文版）,2022(27):121-127

NbFeB

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