回火温度对晶界添加烧结钕铁硼磁体结构演变及磁性提升机理的影响

Effect of Annealing Temperature on Microstructure and Magnetic Properties of Grain Boundary Addition Sintered Nd-Fe-B Magnets

采用晶界添加的方法制备了添加Tb_(65)Cu_(35)的烧结Nd-Fe-B磁体,研究了回火温度对晶界添加磁体微结构演变规律及磁性能的影响,并对其性能提升机制进行了分析。结果表明:经910℃一级回火2 h,460℃二级回火2 h的磁体性能最佳,获得了B_(r)=14.14 k Gs,H_(cj)=12.31 k Oe,(BH)_(max)=47.89 MGOe的磁性能,回火后的磁体的矫顽力从10.21 k Oe提升到12.31 k Oe,增加了约20%,剩磁基本保持不变。矫顽力的提升主要归因于硬磁的(Nd,Tb)-Fe-B壳层以及连续晶界层的形成。通过一阶反转曲线(FORC)对不同回火条件下样品的磁化反转过程进行了分析,可以发现最差回火态晶界添加磁体中有两个峰,然而,最佳回火态的晶界添加磁体只有一个明显的峰,表现出明显的相互作用的单畴晶粒特性,表明最佳回火态磁体内核壳之间具有强的耦合相互作用。

In this paper,sintered Nd-Fe-B magnets with Tb_(65)Cu_(35) were prepared by grain boundary addition.The effect of annealing temperature on microstructure and magnetic properties of the grain boundary addition magnets was systematically studied,and the performance improvement mechanism was analyzed.The results show that the magnet performance has the best first annealing temperature at 910℃for 2 h and secondary annealing temperature at 460℃for 2 h.The coercivity of the magnets after annealing increases from 10.21 to 12.31 kOe,an increase of about 20%,and the remanence remains basically unchanged.The increase in coercivity is attributed to the formation of a hard magnetic(Nd,Tb)-Fe-B shell and a continuous grain boundary layer.The magnetization reversal process of the magnets was analyzed by the first order reversal curve(FORC).It can be found that there are two peaks in the worst annealed-state grain boundary addition magnet.However,for the best annealed-state grain boundary addition magnet,there is only one distinct peak.The results show that the grain boundary addition magnets in the best annealed-state exhibit adistribution of interacting single-domain grains.