Excellent impact resistance of multilayer metallic glass films subjected to micro-ballistic impact by overcoming dynamic size effects

Size effects are key issues that hinder the enhancement of impact resistance of films with increasing thickness. In this paper, we consider Ni₂Ta amorphous metallic alloy as a prototype thin film and demonstrate that the impact resistance of metallic glass (MG) nanofilms with surface oxidation subjected to micro-ballistic impact can be increased significantly by lamination of thin monolayers, overcoming significantly the size effects in the impact resistance of MG nanofilms. Shear band formation and delamination are the dominant energy dissipation mechanisms for multilayered films under impact. Our molecular dynamics (MD) simulations confirmed that the interfaces between thin layers as modified by surface oxidation play an important role in the impact resistance of the multilayered films. Surface oxidation of multilayered films increases significantly the impact resistance due to oxidation-induced curly structure and the increase of the interfacial strength, which contributes greatly to the energy dissipation during impact. However, excessive oxidation initiates defects near the surfaces of the monolayers to therefore reduce greatly impact resistance of the multilayered films. Our work suggests an effective pathway for fabricating high-performance multilayered MG films with extraordinary impact resistance by overcoming the size effects through the lamination of monolayers.