Superhigh strength and good soft-magnetic properties of (Fe,Co)–B–Si–Nb bulk glassy alloys with high glass-forming ability

$\mathrm{Fe}$ -based bulk ferromagnetic glassy alloys with diameters up to $5\mathrm{mm}$ were formed in ${\left[{\left({\mathrm{Fe}}_{1-x}{\mathrm{Co}}_x\right)}_{0.75}{\mathrm{B}}_{0.2}{\mathrm{Si}}_{0.05}\right]}_{96}{\mathrm{Nb}}_4$ system by the copper mold casting method. The substitution of $\mathrm{Co}$ for $\mathrm{Fe}$ caused an increase of glass-forming ability as well as an improvement of mechanical and magnetic properties. The bulk glassy alloys exhibited superhigh fracture strength of $3900–4250\mathrm{MPa}$ , Young’s modulus of $190–210\mathrm{GPa}$ , elastic strain of 0.02, and plastic strain of 0.0025. The bulk glassy alloys also exhibited good soft magnetic properties, i.e., saturation magnetization of $0.84–1.13\mathrm{T}$ , low coercive force of $1.5–2.7\mathrm{A}∕\mathrm{m}$ , high permeability exceeding $1.2\times {10}^4$ , and Curie temperature of $600–690\mathrm{K}$ .