Roles of Y and Fe contents on glass-forming ability, thermal stability, and magnetic properties of Co-based Co–Fe–Y–B bulk metallic glasses

Abstract

Soft magnetic Co-based bulk metallic glasses (BMGs) with large supercooled liquid region (ΔTx) and high saturation magnetic flux density (Bs) have been developed in a new Co–Fe–Y–B alloy system. Addition of appropriate contents of Y and Fe into a Co75B25 alloy enlarges the ΔTx and improves the glass-forming ability (GFA). ΔTx of 50–64 K and a critical diameter of up to 2.0 mm have been achieved for the (Co0.5–0.7Fe0.3–0.5)71.5Y3.5B25 BMGs. The coercivity (Hc) of Co75-xYxB25 and (Co0.7Fe0.3)75-xYxB25 (x = 0–5) alloy series shows a similar V-shape change with Y content, and gets the minimum at x = 3.5, while that of (Co1-yFey)71.5Y3.5B25 (y = 0–0.5) alloys keeps rising with the increase of Fe content. The Bs of the alloys monotonically decreases with more Y addition and increases with enriching of Fe. The (Co0.5–0.7Fe0.3–0.5)71.5Y3.5B25 BMGs exhibit high Bs of 1.00–1.17 T and low Hc of 5.4–6.4 A/m. The BMGs possess high yield strength of 3978–4152 MPa with distinct plastic strain of up to 0.9% and Vickers hardness of 1218–1233 as well. The possible mechanisms of Y and Fe affecting the GFA, thermal stability, and magnetic properties of the Co-based Co–Fe–Y–B metallic glasses have been discussed.