Effect Of SPS And Addition Of Rare Earth Elements On Micro Structure And Properties Of NdFeB Magnets

NdFeB permanent magnet material is a kind of rare earth permanent magnet material with high remanence,high coercive force and high magnetic energy product,which is widely used in computers,aerospace,new energy vehicles and other industries.With the continuous development of new technologies,the requirements for the comprehensive performance of NdFeB permanent magnet materials are also boosted up.Therefore,improving the comprehensive performance of NdFeB magnets is one of topics in this filed.In this paper,nanocrystalline NdFeB magnets with excellent magnetic properties have been prepared by spark plasma sintering technique?SPS?.The rare earth elements and thermal deformation were used to further improve the performance of the magnets.The effect of the microstructure of the magnets on the properties has been studied.The main results are as follows:?1?Based on SPS technology,MQU-M nanocrystalline magnetic powder was used to study the microstructure and magnetic properties of NdFeB magnets at different sintering temperatures.The NdFeB magnet with the best comprehensive magnetic properties was prepared at 650?/50MPa/5min.The remanence,coercivity and magnetic energy product are 0.78T,1350kA/m and 100kJ/m³,respectively.?2?The effect of DyF₃ doped powder on SPS-NdFeB magnets has been studied,and the NdFeB magnet with higher coercivity was obtained.The reason for the increment of coercive force is the diffusion of Dy and the formation of higher anisotropy field?Nd,Dy?2Fe14B phase.The results show that the NdFeB magnets doped with 2wt%DyF₃ and prepared at 650?/50MPa/5min have the best comprehensive magnetic properties.The magnetic properties are Br=0.77T,Hcj=1619kA/m,?BH?max =101.4kJ/m³.The effect of Gd doping on the thermal stability of NdFeB magnets was also investigated.Experiments show that Gd doping is beneficial to the thermal stability of magnets.?3?The precursor prepared by SPS and the DyF₃-doped magnet were subjected to hot deformation technology to obtain an anisotropic NdFeB magnet with excellent magnetic properties and corrosion resistance.Further diffusion of Dy element during hot deformation results in a significant increase in the coercivity of the hot deformed magnet.Among them,the SPS-NdFeB magnet doped with 2wt%DyF₃ has the highest comprehensive magnetic properties after hot deformation,which are Br=1.33 T,Hcj=1225 kA/m,and?BH?_max=286 kJ/m³.