Energy dissipation mechanism of G-phase and L-phase metallic glass nanofilms subjected to high-velocity nano-ballistic impact

The energy dissipation mechanisms of G-phase and L-phase metallic glass nanofilms subjected to high-velocity nano-particle impact were investigated by molecular dynamics (MD) simulations. We identified the phase transition from G-phase to L-phase in which the locally ordered core structures transform to liquid-like structures due to local mechanical melting and adiabatic heating of the G-phase under high strain rate impact. The appearance of phase transition provides a new channel for energy dissipation, thus the relatively thicker G-phase nanofilm with ordered core structures has a higher specific energy absorption compared with the L-phase film at the same thickness and impact velocity. However, if the thickness decreases below the characteristic length scale of the heterogeneous structure, the broken core structures in the G-phase films act as prefabricated defects that fail prematurely when subjected to impact, resulting in less impact resistance of the G-phase film compared to the L-phase film. This paper provides a useful method for improving the impact resistance of metallic glass films by tailoring the microstructures.