磁粉粒径对烧结Nd-Fe-B磁性能和初始磁导率的影响

Effect of Particle Size on the Magnetic Properties and Initial Permeability of Sintered Nd-Fe-B Magnets

采用粉末冶金法制备了名义成分为(Pr_(25)Nd_(75))_(25)Dy_6Al_(0.5)B_1Co_1Cu_(0.2)Fe_(bal)的烧结Nd-Fe-B磁体,并研究了不同粒径磁粉制备的烧结Nd-Fe-B磁体磁性能和初始磁化阶段最大磁导率的相应演变规律。结果表明,磁粉平均尺寸为3.0μm时对应的磁体的内禀矫顽力最大,磁粉平均尺寸为3.5μm时对应的磁体的剩磁最高。从磁体的微观结构观察和性能测试发现,磁粉粒径为3.0μm时,烧结磁体主相更加规则、均匀,提高了磁体的矫顽力。随着磁粉平均尺寸进一步减小,磁粉粒径为2.5μm时,富Nd相以氧化物形式发生了团聚,且分布不均匀,磁体晶界出现孔洞,去磁耦合效率下降,导致磁体矫顽力降低;磁体氧含量随着磁粉平均尺寸的减小而增大,磁体内杂质相增多,剩磁下降;增多的杂质相使得磁化初始阶段的最大磁导率降低。

The Nd-Fe-B magnet with nominal composition of (Pr25Nd75)25Dy6Al0.5B1Co1Cu0.2Febal was prepared by a traditional powder metallurgy method. The magnetic properties and initial magnetization permeability of the Nd-Fe-B from magnetic powders with different particle sizes were investigated. The results show that the magnet from the particles with an average size of 3.0 μm achieves the best Hcj,and the particles with an average size of 3.5 μm obtains the best Br. The refined particle size of 3.0 μm makes the morphology regular and uniform. But as the average particle size further decreases, the Nd rich phase is in the form of an oxide and unevenly distributed at the grain boundary, and the demagnetization coupling efficiency drops, resulting in a decrease in Hcj. The oxygen content increases as the average size becomes smaller, and Br decreases as the impurity content increases. On the other hand, the initial permeability dramatically falls with the increasing impurity content.