Enhanced ductility by stress confinement in multilayered glassy thin films

The deformation of metallic glasses (MGs) is characterized by strong strain localizations in shear bands and rapid propagation thereof, leading to brittle fracture. The incorporation of secondary phases or heterogeneities into the glassy structure has been shown to enhance ductility, resulting in the formation of metallic glass composites (MGCs). In this study, we examine the deformation behavior of MGCs composed of two distinct glassy phases applying in-situ deformation combined with 4D scanning transmission electron microscopy (4D-STEM). Local strain evolution was tracked during loading and revealed that nanolayered MGCs exhibit significantly enhanced plasticity compared to monolithic glasses. This improvement of ductility was attributed to a notable confinement of atomic strain in the soft layer, which is enabled by the layered architecture. Notably, confining stress within individual layers suppresses the development of mature shear bands and delays the onset of critical shear instabilities. Complementary molecular dynamics simulations support experimental results, clarifying how architectural confinement and phase synergy can be utilized to enhance the mechanical properties of two-phase glassy materials.