Thermal Stability and Soft Magnetic Properties of (Fe, Co)-(Nd, Dy)-B Glassy Alloys with High Boron Concentrations

Abstract

Fe-based glassy alloys with high boron concentrations in (Fe, Co)–(Nd, Dy)–B system were found to exhibit a large supercooled liquid region (∆Tx) and good soft magnetic properties. The Fe62Co9.5Nd3Dy0.5B25 glassy alloy with ∆Tx of 56 K exhibits high saturation magnetization ( Is) of 1.41 T, low coercive force ( Hc) of 2.6 A/m and large permeability (µe) at 1 kHz of 12000. The Fe62Co9.5Nd3Dy0.5B25 glassy alloy rods were produced in the diameter range up to 0.75 mm by copper mold casting. The substitution of 2 at% elements TM (TM = Nb, Ta, Mo and W) for Fe and Co, remarkably increases the ∆Tx and Tg/Tl, leading to an increase in the glass-formation ability (GFA) for Fe60.3Co9.2Nd3Dy0.5B25TM2. The ∆Tx and Tg/Tl increase from 56 to 87 K and 0.56 to 0.57, respectively, and the glassy alloy rods were produced in the diameter range up to 1.2 mm. The saturation magnetization Is decreases slightly, while the coercive force Hc remains almost unchanged by the addition of 2 at% TM elements.