Evolution of Mechanical Anisotropy in Nano-scale Metallic-glass thin Films Under Indentation

The mechanical behavior of Cu-Zr-Al metallic-glass thin films under indentation was studied with the molecular dynamics simulation methodology to investigate changes of microstructures through degrees of elastic anisotropy. In this work, the (Cu50Zr50)100-xAlx, where x is measured by atomic percentage, was studied by molecular dynamics (MD) simulation. Our metallic-glass models were first sputter-deposited on crystalline substrate by MD with consideration argon working gas. The interaction between argon working gas and metallic atoms was modeled by the pair-wise Moliere potential. The as-deposited films were amorphous after equilibration, and their mechanical properties were characterized by ultra-nano-indentation simulations by MD with a right-angle diamond conical indenter tip, as well as a strain perturbation method to identify full elastic constants under the tip. Through region-by-region probes of the elastic properties of the film after being indented, it is found that local elastic anisotropy changes in relation to locations and penetration depth.