Enhancement of plastic deformation in FeCoNbB bulk metallic glass with superhigh strength

► The effect of B content on GFA of (Fe0.5Co0.5)71−xNb6B23+x BMGs was investigated. ► Fe33.5Co33.5Nb6B27 BMG with critical diameter of 3 mm was synthesized. ► Fe33.5Co33.5Nb6B27 BMG also shows high σy of 4860 MPa and ɛp of 1.4%. ► Addition of 0.1 at.% Cu can enhance ɛp to 3.7% without obvious decrease of σy.