FABRICATION OF NANOCRYSTALLINE FE86ZR7B6CU1 SOFT-MAGNETIC COMPACTS WITH HIGH SATURATION MAGNETIZATION

Soft-magnetic cores with nanoscale bcc structure were fabricated by consolidation of amorphous or nanocrystalline Fe86Zr7B6Cu1 (at.%) powder using a hot-pressing machine. The most appropriate process to fabricate nanocrystalline Fe86Zr7B6Cu1 soft-magnetic compacts with high density is the direct consolidation of the amorphous powder into nanocrystalline compacts. This process is superior to the annealing method of the amorphous compacts produced from the amorphous powder. The main reason is that the former process fully utilizes the low viscosity of the amorphous alloy before the crystallization temperature. On the other hand, the consolidation of the nanocrystalline powder prepared by annealing of the amorphous powder is an unsuitable process because of the lack of the decrease in viscosity. The nanocrystalline Fe86Zr7B6Cu1 compact obtained by pressing the amorphous powder for 200 s at 853 K and 1.5 GPa has a high density of 99.9% of the theoretical density and exhibits good soft-magnetic properties. The saturation magnetization B-s, coercive force H-c, maximum permeability mu(max), effective permeability mu(e) at 1 kHz and 0.8 A/m, and core loss W-h at 10 kHz and 0.1 T are 1.56 T, 33 A/m, 4300, 1300, and 37 W/kg, respectively. It is therefore established that the present compact possesses good soft-magnetic properties combined with high magnetization.