Plasticity enhancement of a Zr-based bulk metallic glass by an electroplated Cu/Ni bilayered coating

In this study, the effect of a Cu/Ni bilayered coating on the shear banding behavior and compressive plasticity of a Zr-based bulk metallic glass (BMG) was investigated. As compared to a mono-layered Cu or Ni coating, the Cu/Ni bilayered coating has provided a better geometric confinement effect. Through a detailed comparative analysis among coated BMG samples with different plasticity, the correlation between the macroscopic plastic deformation behavior and the serrated flow characteristics is studied from the potential energy landscape point of view. The comparatively longer hanging time and larger elastic energy density in the Cu/Ni coated BMG in the serrated plastic regime result in an increased global plastic strain of ∼11.2%. The enhanced plasticity is attributed to the thin soft Cu layer acting as a buffer zone for absorbing the elastic energy upon loading, and the strong outer Ni coating exerting a high confining stress upon loading, which impede the rapid propagation of the shear bands. In addition, the strong Cu-Ni interface is believed to contribute to the enhanced plasticity.