摘要
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 transmission electron microscopy images revealed that the Nb element gathered on the grain boundary and triple grain boundary to form c-Nb and h-Nb Fe B to hinder the grain growth during the hot-deformation process,which led to direct enhancement in the coercivity.Furthermore,the c-Nb and h-Nb Fe B are nonmagnetic phases that strengthened the magnetic isolation.However,the h-Nb Fe B precipitated from the hard magnetic phase and formed crystal defects which led to remanence deterioration.
基金
supported by the Major Project of“Science and Technology Innovation 2025 in Ningbo City(Nos.2020Z064,2019B10093)
the Basic research expenses for provincial universities of Zhejiang Ocean University(No.2019J00036)
the Talent introduction research fund of Zhejiang Ocean University(Nos.xjrcyj201801,11045091021)。
