(Co1−xFex)68B21.9Si5.1Nb5 bulk glassy alloys with high glass-forming ability, excellent soft-magnetic properties and superhigh fracture strength

► We studied the influence of Co to Fe ratio on GFA, magnetic properties and σf. ► CoFeBSiNb BGAs with with diameters up to 5.5 mm were synthesized. ► The alloys exhibit good soft-magnetic properties and superhigh σf.►Hc, μe and Is of these glassy alloys are 0.71-1.58 A/m, 22,100-32,500 and 0.49-0.91 T. ► The σf of these glassy alloys are 4250-4450 MPa.