Novel Soft Magnetic Co-Based Ternary Co–Er–B Bulk Metallic Glasses

In this work, a series of Co-based ternary Co–Er–B bulk metallic glasses (BMGs) with excellent soft magnetic properties and high strength were developed, and the local atomic structure of a typical Co_71.5Er_3.5B₂₅ metallic glass was studied through in situ high-energy synchrotron X-ray diffraction and ab initio molecular dynamics simulations. The results reveal that the BMG samples can be obtained in a composition region of Co_68.5–71.5Er_3.5–4B_25–27.5 by a conventional copper-mold casting method. The Co–Er–B metallic glasses possess stronger atomic bond strengths and denser local atomic packing structure composed of a higher fraction of icosahedral-like clusters but fewer deformed body-centered cubic and crystal-like polyhedrons, and they exhibit slower atomic diffusion behaviors during solidification, as compared to Co–Y–B counterparts. The enhancement in structural stability and the retardation of atomic-ordered diffusion lead to the better glass-forming ability of the Co–Er–B alloys. The smaller magnetic anisotropy energy in the Co–Er–B metallic glasses results in a lower coercivity of less than 1.3 A/m. The Co–Er–B BMGs exhibit high-yield strength of 3560–3969 MPa along with distinct plasticity of around 0.50%.