低压烧结对NdFeB磁体微观结构与服役稳定性的影响

Effect of Low-Pressure Sintering on Microstructure and Service Stability of NdFeB Magnets

研究了NdFeB磁体微观结构和服役稳定性的内在联系。结果表明,低压烧结NdFeB磁体具有更加细小的晶粒尺寸和分布更为均匀的晶间富钕相,有利于磁体获得更小的矫顽力温度系数,从而提高其温度稳定性。对比真空烧结后的磁体,低压烧结磁体的矫顽力温度系数从-0.488%/℃减小至-0.472%/℃。但是富钕相从三角晶界向主相晶间流动形成了完整的网状结构,不利于磁体的耐腐蚀性能。低压烧结磁体在3.5%(质量分数)NaCl溶液中浸泡后腐蚀失重更为严重,表现出更强的腐蚀倾向。

The internal relationship between the microstructure and service stability of NdFeB magnets was investigated.Results show that the NdFeB magnets after low-pressure sintering have significantly finer grains and more uniform distribution of the Nd-rich phase among the grains,which is beneficial to obtain smaller coercivity temperature coefficients of magnets,thereby improving the temperature stability.Compared with that of the magnets after vacuum sintering,the coercivity temperature coefficient of lowpressure-sintered magnets is reduced from-0.488%/°C to-0.472%/°C.However,the flow of the Nd-rich phase from the triangular grain boundary to the main phase intergranular area promotes the formation of complete network structure,which degrades the corrosion resistance of the magnets.The low-pressure-sintered magnets show more serious corrosion mass loss after immersion in 3.5wt%NaCl solution,presenting a stronger corrosion tendency.