Strain localization in amorphous films deposited on rough substrates

In this study, calculations are carried out for the plastic deformation of amorphous metallic glass films resting on rough substrates. It is found that plastic strain localization in the amorphous film is controlled by the synergistic interplay between substrate constraint and interfacial debonding. For the polymer substrate with low stiffness and yield stress, film-substrate interfacial debonding has negligible influence on plastic deformation of amorphous film. However, in the case of metal substrate with high stiffness and yield stress, debonding of the film-substrate interface promotes plastic strain localization in the amorphous film, leading to low plastic dissipation. The interface morphology plays an important role in development of shear bands in the amorphous film; high degree of interface waviness enables formation of multiple shear bands in the amorphous film, delaying strain localization and promoting plastic dissipation. We have further unraveled the effect of adding a buffer layer in the structure consisting of the amorphous film and rough substrate. The wavy interface is capable of generating inhomogeneous plastic deformation of the buffer layer, which activates strain localization bands in the amorphous film. The buffer layer with high stiffness suppresses strain localization in the amorphous film.