Fabrication of Nanocrystalline Soft-Magnetic Bulk Cores through

本文研究了采用粉末烧结法制备具有高饱和磁化强度和良好软磁性能的Fe-（Zr，Nb，Hf）-B纳米晶合金的纳米晶bcc结构软磁块体磁芯。(1)在约100 K的机械破碎的熔体快淬非晶薄带，退火脆化，有效地产生非晶粉末。另一方面，通过冷却速率不足以获得非晶相的高压气体雾化没有获得非晶粉末。(2)通过单轴热压技术或温挤压技术将非晶粉末直接固结，获得了密度大于99.5%的纳米晶压坯。相反，通过对非晶粉末进行退火制备的纳米晶粉末的固结不适合于生产具有高密度的纳米晶压坯，导致纳米晶压坯的密度低于90%。(3)纳米晶Fe-Zr-B-Ni压坯的磁致伸缩为零，抑制了残余应变对软磁性能的影响，获得了最佳的软磁性能。在<88>1 kHz和0.4 A/m下，纳米晶Fe_ Zr_7B_3Ni_2压坯的饱和磁化强度B_s为1.58 T，矫顽力H_c为14 A/m，有效磁导率μ_e为2000，密度接近99.9%. (4)采用溶胶-凝胶法在非晶粉末颗粒表面包覆一层SiO_2薄膜，提高了纳米晶压坯的软磁性能。因此，通过对粉末颗粒进行电绝缘，减少了涡流损耗，因此可以合理地得出结论，非晶粉末的固结将促进软磁体芯的进一步发展。

We have investigated synthesize of soft-magnetic bulk cores with nanocrystalline bcc structure by powder consolidation for Fe-(Zr, Nb, Hf)-B nanocrystalline alloys with both high saturation magnetization and good soft-magnetic properties.(1) Amorphous powder was effectively produced by mechanically crushing at about 100 K the melt-spun amorphous ribbons which were embrittled by annealing. On the other hand, no amorphous powder was obtained by a high-pressure gas atomization where the cooling rate was insufficient for obtaining amorphous phase.(2) Nanocrystalline compacts with high densities above 99.5% were obtained by the direct consolidation of the amorphous powders through a uniaxial hot-pressing technique or warm extrusion. On the contrary, the consolidation of nanocrystalline powders which were prepared by annealing the amorphous powder was unsuitable for production of nanocrystalline compacts with high density, resulting in nanocrystaline compacts with a densities below 90 %.(3) The best soft-magnetic properties were obtained in a nanocrystalline Fe-Zr-B-Ni compact, where the deterioration of the soft-magnetic properties by residual strain was suppressed because of the its zero magnetostriction. The nanocrystalline Fe_<88>Zr_7B_3Ni_2 compact with a nearly full density of 99.9% exhibited the saturation magnetization B_s of 1.58T,coercive force H_c of 14A/m and effective permeability mu_e of 2000 at 1 kHz and 0.4 A/m.(4) The soft-magnetic properties of the nanocrystalline compacts were improved by coating the amorphous powder particles with SiO_2 thin films using sol-gel method. It is for this reason that eddy current loss is reduced by electrically insulating the powder particles.We may, therefore, reasonably conclude that the consolidation of amorphous powders will promote the further development of soft-magnetic bulk cores.