The Effects Of Adding Tb Alloy And Its Oxides At Grain Boundaries On The Microstructure And Properties Of Sintered Nd-Fe-B Solid Waste

Research on the recovery and reuse of Nd-Fe-B solid waste,mainly adopts the reuse method of doping trace heavy rare earth Tb alloy and its oxide on Nd-Fe-B powder prepared by hydrogenation recovery process of sintered Nd-Fe-B solid waste obtain regenerated sintered Nd-Fe-B magnets,and analyze the microstructure and performance of the magnets.Optimize from sintered Nd-Fe-B waste to regenerated magnetic powder,develop and verify a complete recycling process for sintered Nd-Fe-B regenerative magnets,and develop sintered Nd-Fe-B regenerative magnets with excellent magnetic properties and other performance.The main research conclusions include the following three aspects:The effects of adding low-melting-point Tb_71.5Fe_28.5 alloy on grain boundaries on the magnetic properties,corrosion resistance and microstructure of sintered Nd-Fe-B regenerative magnets were explored through experiments.The study found that when the addition of Tb_71.5Fe_28.5 alloy increased from 0wt%to 0.9wt%,the magnetic properties of the magnet increased from the initial 17.30 k Oe to 20.68 k Oe at 0.6 wt%,an increase of 19.54%.Combined with the microstructure analysis,the performance improvement is mainly due to the optimization of the microstructure.The test results of polarization curves show that the anti-corrosion performance of the magnet has also been significantly improved.The influence of Tb₂Fe₁₂Ga₅ alloy with a melting point of 874.7℃on the magnetic properties and corrosion resistance of sintered Nd-Fe-B regenerative magnets under different addition conditions was explored.The effect of Ga element on the grain boundary and performance of the magnet was compared under the changing conditions.According to the results,the coercive force of 3 wt%Nd-Fe-B regenerated magnets increased from the initial16.85 k Oe to 18.61 k Oe,which was 10.45%higher than the initial coercive force.The corrosion resistance of regenerative magnets is also significantly enhanced.The effects of adding Tb₄O₇ on the grain boundary on the magnetic properties,corrosion resistance and microstructure of sintered Nd-Fe-B regenerative magnets were analyzed through experiments.The difference in the mechanism of influence of Tb oxide and its alloy on the microstructure and performance of magnets was analyzed.According to the experimental results,the coercive force of the magnet increases from 17.61 k Oe of the initial magnet to 20.22 k Oe with 0.6 wt%addition,an increase of 14.82%.The improvement of magnetic properties is due to the reaction between Tb₄O₇ and the main phase to generate a（Nd,Tb）₂Fe₁₄B magnetically hardened layer with a higher anisotropy field.However,microscopic analysis shows that too much Tb₄O₇ addition will reduce the density of the magnet at the same sintering temperature and deteriorate the microstructure.