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

The effect of B on the glass-forming ability of FeCoNbB alloys was investigated. Bulk metallic glasses with critical diameters up to 3 mm and superhigh yield strength of 4860 MPa were synthesized in (Fe0.5Co0.5)71−xNb6B23+x (x = 0, 2, 3, 4 and 5) alloy system. Besides, Cu was added to the Fe33.5Co33.5Nb6B27 alloy with the aim at enhancing mechanical properties, and it was found that proper amount of Cu addition could effectively improve the compressive plasticity from 1.4% to 3.7% without obvious strength decreasing. The enhancement of plasticity is ascribed to the formation of clusters in Cu-contained FeCoNbB bulk metallic glasses.