Response of an amorphous/crystalline interface to nanoindentation: an atomistic study

Abstract

We perform molecular dynamics simulations of nanoindentation in bilayer systems composed of a Cu64.5Zr35.5 metallic glass and a pure Cu crystalline sample. Both the cases where the glass and where the crystal is top are studied. We find a strong asymmetry in the response of the glass-top and the crystal-top system. The crystal-top system is the weakest one. Here, dislocations nucleate at the interface and also induce considerable strain in the glass layer beneath; hence the interface acts to reduce the plastic activity in the top crystal layer. In contrast, the glass-top system is the hardest system of the four systems studied. Shear bands form considerably earlier in the glass-top system than in a pure glass. The interface hinders shear band propagation; it thus causes a deflection of the load exerted by the indenter and hardens the material. Dislocations in the bottom crystal can be generated only when the indenter has penetrated the interface.