ABSTRACT

Hot-deformed anisotropic Nd-Fe-B magnets may potentially attain high coercivity due to their fine and highly orientated crystal grain microstructure as a result of the unique production process that creates these magnets. However, despite their fine grain size of 100–500 nm, coercivity was only around 25% of the full potential of the anisotropy field. This grain size was close to the critical diameter of the single domain grain size of the Nd-Fe-B magnet. This study investigated the effects of chemical composition and deformation conditions on the magnetic properties of Nd-Fe-B magnets, observing their microstructure to obtain guidance on the ideal microstructure. We also improved the hot-deformation technique in parallel to optimize microstructure by controlling the compositions and hot-deformation conditions based on the results of basic studies. Lastly, we fabricated heavy rare-earth-free magnets with a coercivity exceeding 1600 kA/m (20 kOe), which is 20% higher than that of conventional magnets.

摘要

热变形的各向异性Nd-Fe-B磁体由于其独特的生产工艺而具有精细且高度取向的晶粒微观结构，因此有可能获得高矫顽力。然而，尽管它们具有100-500 nm的细晶粒尺寸，但矫顽力仅约为各向异性场全部电势的25％。该晶粒尺寸接近Nd-Fe-B磁体的单畴晶粒尺寸的临界直径。这项研究调查了化学成分和变形条件对Nd-Fe-B磁体磁性能的影响，观察了它们的微观结构，从而为理想的微观结构提供了指导。我们还根据基础研究的结果，通过控制成分和热变形条件，并行改进了热变形技术，以优化微观结构。