Intrinsic size effects in the mechanical response of taper-free nanopillars of metallic glass

Both quantitative stress-strain curves and in situ transmission electron microscope observations demonstrate intrinsically strong sample size effects on the deformation mode of taper-free metallic glass pillars. With the pillar diameter gradually decreasing from 640 to 70 nm, the deformation mode evolves from (i) highly localized and catastrophic shear banding to, (ii) initially nonlocalized deformation developing toward stop-and-go shear banding accompanied by softening, (iii) apparently homogeneous and banding-less deformation but with intermittent shear events, and eventually (iv) fully homogeneous and smooth plastic flow.