晶界扩散Dy–Al–Ga对钕铁硼磁体的磁性能和微观组织的影响

通过晶界扩散Dy70Al10Ga20合金研究了烧结Nd-Fe-B磁体的磁性能和热稳定性能.用NIM-500C高温永磁测量仪和MLA650扫描电镜测出了磁体在扩散前后的磁性能和微观组织的变化.结果表明,在Dy70Al10Ga20合金扩散热处理后,磁体矫顽力从原始的1080.968kA/m显著提升到1671.600kA/m,提升幅度约为55%,而剩磁下降很少.Dy、Al、Ga元素在晶界处扩散,很好地隔绝了磁交换作用,提升矫顽力.SEM图显示在扩散Dy70Al10Ga20合金后,可以很明显地看到晶粒外延层有一层灰色的壳层包覆着主相晶粒,很好地起到了隔离晶粒的磁交换作用.XRD显示主相的峰普遍往右偏移,这归因于重稀土元素Dy进入晶粒外延层形成(Nd,Dy)2Fe14B核壳结构.Dy的原子半径比Nd小,导致峰往右移.

Effect of grain boundary diffusing Dy-Al-Ga on the microstructure and magnetic properties of NdFeB magnets

The magnetic properties and thermal stability of sintered Nd-Fe-B magnets were studied by grain boundary diffusing Dy₇₀Al₁₀Ga₂₀ alloy. The changes of magnetic properties and microstructure of the magnets were measured by NIM-500 C and SEM. The results show that after Dy₇₀Al₁₀Ga₂₀ alloy receiving thermal diffusion treatment, its coercivity is enhanced significantly from 1 080.968 kA/m to 1 671.600 kA/m, a striking increment of 55 %. And there is only a slight reduction in remanence. Dy, Al and Ga elements diffuse at the grain boundary, which effectively insulates magnetic exchange so that the coercivity of the alloy is well improved. It is obvious that after Dy₇₀Al₁₀Ga₂₀ alloy is diffused, in the epitaxial layer of grains is a gray shell covering the main phase grains via SEM, which plays an active role in magnetic exchange to isolate the grains. The peak of the main phase is generally shifted to the right via XRD observation, given the fact that the heavy rare earth element Dy enters the epitaxial layer of grains and forms the (Nd, Dy) core shell structure. The atomic radius of Dy is smaller than that of Nd, causing the peak to move to the right.