Design strategy for high plasticity and strength in metallic glasses: A molecular dynamics simulation study

The poor plasticity of metallic glasses (MGs) limits their application as structural materials. How to enhance dramatically the plasticity of the MGs without compromising the strength is a highly attractive topic. Here, the effect of layer thicknesses and analogous flow defects concentrations (AFDCs) on the mechanical behavior of amorphous/amorphous (A1/A2) nano-multilayers is investigated by molecular dynamics method. The results indicate, when layer thickness is small (from 1.8 to 8.5 nm), for any given layer thickness, the plastic deformation of A1/A2 nano-multilayer evolves from a “shear localization” fashion to a “uniform deformation” mode, and eventually to a “shear localization” deformation again with the increase of AFDC. Comparing with the monolithic MGs, the A1/A2 nano-multilayers with optimum AFDC manifesting uniform deformation achieve a perfect combination of high strength and superior plasticity. What is more, the optimum AFDC could always be found for the sample with arbitrary layer thickness, and shows an upward tendency with increasing layer thickness. When layer thickness is large (13.0 and 25.0 nm), no matter how the AFDC changes, the optimum AFDC disappears for determined layer thickness. In this case, the plastic deformation behavior is arrested in A1 soft layer, resulting in intense shear localization and the reduced plasticity.