Deformation behaviour of amorphous Fe-Ni-W/Ni bilayer-confined bulk metallic glasses

Abstract

In this study, an amorphous Fe-Ni-W/Ni bilayer was successfully electroplated on a Zr-based bulk metallic glass (BMG), and the deformation behaviour of the bilayer-coating-confined BMG was investigated. The findings show that the macroscopic plasticity of the BMGs was enhanced from 1.3 % to 10.7 %. More importantly, bilayer-confined BMGs have a large plateau of the serrated flow with an insignificant decrement before failure. When characterizing the serrated flows of both uncoated and bilayer-confined BMGs by introducing absolute values of stress raises/drops, smaller amplitudes of stress drops as well as a larger stress-drop frequency during the plastic-deformation stage were found in the bilayer-confined BMGs. The origin of the increased stable plastic flow was discussed, and it is mainly attributed to the enhanced confinement caused by the introduction of the amorphous layer. The findings are significant for enhancing the macroscopic plasticity of the BMGs and for understanding the deformation mechanism of the serrated plastic flow in geometrically confined BMGs.