A comparative study of the rate effect on deformation mode in ductile and brittle bulk metallic glasses

The rate effect on the deformation mode of bulk metallic glasses (BMGs) is investigated by a comparative study between ductile and brittle compositions via real-time photographing. The strain-rate controls the deformation mode transition from shear-dominated sliding under quasi-static compression to cracking-dominated fracture under dynamic compression. In ductile BMGs, progressive sliding occurs at lower strain rate and contributes to a stable deformation manner. In brittle BMGs, however, unstable deformation occurs through rapid sliding even under quasi-static compression. Both ductile and brittle BMGs undergo unstable deformation under dynamic compression. The rate-dependent and composition-dependent tendency of stable or unstable deformation is well characterized by a model based on the ratio of the applied strain energy to the critical dissipation energy at the local shear banding region.