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 Susceptibility of Sintered Nd–Fe–B Magnets

摘要:

本文采用粉末冶金方法制备了名义成分为(Pr₂₅Nd₇₅)₂₅Dy₆Al_0.5B₁Co₁Cu_0.2Fe_bal.的烧结Nd-Fe-B磁体,并研究了不同磁粉粒径制备的烧结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3.0 μm时对应的磁体的内禀矫顽力最好,磁粉平均尺寸为3.5 μm 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。随着平均磁粉尺寸进一步减小,磁粉粒径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。

Abstract:

Particle refinement is the effective way to improve the coercive force without increasing the HRE content in Sintered Nd-Fe-B magnets. The magnetic properties and initial magnetization permeability has been investigated in order to correlate the particle refinement by traditional powder metallurgy method with nominal composition of (Pr₂₅Nd₇₅)₂₅Dy₆Al_0.5B₁Co₁Cu_0.2Fe_bal sintered Nd-Fe-B magnet. The particles with average size of 3.0 μm achieved the best Hcj, and the particles with average size of 3.5 μm obtained the best Br respectively. Refined particle size which made the morphology regular and uniform. But with further decreased the average particle size, Nd rich phase was in the form of oxide, and unevened distribution in the grain boundary, and the demagnetization coupling efficiency droped, results in the decrease of Hcj. The oxidation content increased with the average size becoming samller, the Br decreased with the impurity content increased. On the other hand,the initial permeability dramatically fallen with the impurity content.