Magnetic properties and power losses in Fe–Co-based bulk metallic glasses

Abstract

Magnetic properties of Fe–Co-based bulk metallic glasses have been experimentally investigated. Samples were prepared by water-cooled Cu-mold injection casting technique. The samples have cylindrical shapes with 0.8 mm diameter and 30 mm length. Amorphous structures were confirmed by the presence of a main halo in X-ray diffraction patterns and by the detection of crystallization signal around 650 °C using differential scanning calorimetry. Owing to their amorphous structure, these materials present good soft magnetic properties with coercivity below 100 A/m and magnetic induction around 1.0 T in quasi-static conditions. Hysteresis loops were measured using a digital wattmeter with controlled induction waveform. Power losses were analyzed for the following compositions: [(Fe 1− x Co x ) 75B 20Si 5] 93Nb 4Y 3 ( x=0, 0.2, 0.4, 0.5 and 0.6) over a range of frequencies from 1 to 400 Hz at selected fixed peak inductions. Co addition has shown to improve the soft magnetic properties when x=0.2, 0.4 and 0.5, decreasing coercive fields and power losses, while the magnetic induction is slightly increased (except for x=0.5). Further Co addition ( x=0.6) is detrimental for the soft magnetic properties due to the presence of crystalline α-Fe–(Co) and boride phases. The frequency dependence of power losses was described using a separation theory. It has been observed that an f 1/2 rule is in good agreement with the experimental data.