Magnetic properties of soft magnetic composites fabricated from amorphous Fe73Si11B11C3Cr2 powder by hot pressing under a low pressure

Amorphous Fe73Si11B11C3Cr2 powders were coated with a layer of Fe3O4 through hydrothermal reactions. The coated powder was used to fabricate soft magnetic composites (SMCs) in which the eddy current was confined in individual amorphous particles by the insulating Fe3O4 layer, and the magnetic diluting effect, caused by non-magnetic insulating layer and widely reported in previous research, can be avoided, thanks to the ferromagnetic properties of Fe3O4. The results indicated that when the coated powder was hot-pressed at temperatures near the glass transformation temperature of the metallic glass powder, SMCs with high density and good magnetic properties could be obtained under a low pressure of 600 MPa. The SMCs fabricated at 430 °C exhibited the best magnetic properties, having an effective permeability of 41(at 100 kHz) and a core loss of 707 kW/m3 (at 100 kHz, 50 mT). The properties could be further improved after the sample was annealed at 430 °C to release the internal stresses generated in hot pressing. As a result, the effective permeability was increased to 43(at 100 kHz) and the core loss was reduced to 498 kW/m3 (at 100 kHz, 50 mT) for the annealed sample.