Fabrication and characterization of novel soft magnetic [(Fe0.7Co0.3)71.2B24Y4.8]96Nb4/V2O5 bulk metallic glassy/composite cores with excellent magnetic permeability and low core losses

Abstract

In the present work, fabrication, characterization and magnetic properties of novel soft magnetic composites (SMCs) based on V2O5 insulated [(Fe0.7Co0.3)71.2B24Y4.8]96Nb4 glassy particles are investigated. The uncoated glassy particles, consolidated at an optimized temperature of 893 K, yield bulk metallic glasses (BMGs) exhibiting a high relative density of 99.5%, a wide supercooled liquid region (SLR) of 92 K, a high initial magnetic permeability of 4310, and a notably low coercivity of 35 A/m. The Fe-based glassy particles in the SMCs are uniformly coated by V2O5 insulation, with negligible interfacial reaction or decomposition of the insulation upon hot consolidation. Additionally, the composite samples, particularly with 5 vol% V2O5, display a high thermal stability comparable to monolithic glassy cores. The V2O5 coated glassy particles preserve their excellent thermoplastic formability and densification behavior upon consolidation, resulting in formation of SMCs with a high relative density (98.5–99%). The prepared composites present a low coercivity (79–100 A/m) and a considerably higher initial permeability (425–475) at 1 kHz compared to most other SMCs prepared before. Furthermore, the performed V2O5 insulation enhances the frequency stability of the initial permeability and increases the relaxation frequency from 700 Hz for glassy cores up to 18 kHz for the composites. Magnetic loss separation analysis reveals negligible excess losses of the samples, while larger hysteresis losses are found for the composite cores up to 2 kHz. The composites with 5 vol% V2O5 exhibit about 55% smaller eddy current losses and 47% lower total core losses at 2 kHz than that of glassy cores. The obtained results suggest that the new composite cores are promising soft magnetic materials for medium frequency range electromagnetic applications.