Extraordinary enhancement of the toughness and plasticity of multilayered metallic glass composites with gradient heterogeneous interfaces

A strategy is proposed to enhance the mechanical properties of metallic glasses using multilayered composites with various initial free-volume gradient interfaces and validated by finite element modelling. We found that the ductility of the composites improves significantly with the increasing number of layers. The main factors and the underlying mechanisms are (a) the gradient interface with varying free volume densities that can reduce the local stress concentration, (b) size effects imposed by the layer thickness that limits the local shear and shear bands to grow critically longer and thicker to cause catastrophic failure, (c) the presence of interface barriers to increase the probability of blocking and retarding the shear banding, and (d) the heterogeneity introduced by the statistical distribution of free volumes. The results demonstrate that the multilayered composites are promising in solving the strength-ductility tradeoff in metallic glasses.