Layer thickness effects on the strengthening and toughening mechanisms in metallic glass-graphene nanolaminates

Abstract

Experiments have proved that one solution to improve the ductility of metallic glasses lies in introducing graphene and synthesizing metallic glass (MG) nanolaminates. In this work, molecular dynamic simulations are conducted to investigate layer thickness effects on the tensile behaviors of Cu50Zr50 metallic glass-graphene nanolaminates (MGGNLs). The increase in MG layer thickness leads to the decrease in the ultimate strength of MGGNL and helps to the development of shear bands. Meanwhile, plastic deformation mode transits from homogeneous flow to shear localization. The critical layer thickness related to such a transition can be predicted by the strain energy theory. Once the dissipated energy in MG matrix during shear bands formation exceeds the stored strain energy in graphene, shear localization dominates plastic deformation mode. Besides, fracture strain decreases with increasing MG layer thickness. There also exists a kink for the linear decline in fracture strain, corresponding to the plastic deformation transition. Finally, the equivalent model for layer thickness is proposed to better describe the Hall-Petch effect on the yield strength of MGGNLs. Our study provides the guidance to the synthesis of novel metallic glass nanocomposites.