Enhanced plasticity of FeCoBSiNb bulk glassy alloys by controlling the structure heterogeneity with Cu addition

Abstract In this work, an FeCoBSiNbCu bulk glassy alloy (BGA) with a diameter up to 4 mm was successfully prepared by copper mold casting method. The (Fe 0.5 Co 0.5 ) 71.6 B 20 Si 4 Nb 4 Cu 0.4 BGA exhibits a high strength over 4 GPa and an enhanced plasticity of 3.7%, combined with good soft magnetic properties. A well-developed vein pattern on the fracture surface and highly dense multiple shear bands throughout the overall rod were observed on the deformed specimen. The improved plasticity is strongly related to the nano-scale heterogeneous structure introduced to the glassy alloy by phase separation with minor Cu addition, which can hinder the propagation of shear bands, promote multiple shearing and enhance the plasticity. This work might have a guiding significance for a deep-understanding of the plastic deformation mechanism of Fe-based BGA in a high strength level.