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

Soft magnetic Co-based bulk metallic glasses (BMGs) with large supercooled liquid region (?Tx) 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 ?Tx and improves the glass-forming ability (GFA). ?Tx 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 (Co1yFey)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.

Automated summary

Soft magnetic Co-based bulk metallic glasses with large supercooled liquid region and high saturation magnetic flux density have been developed in a new Co-Fe-Y-B alloy system. Addition of appropriate contents of Y and Fe into the alloy can enlarge the supercooled liquid region and improve the glass-forming ability, leading to high magnetic properties.