Notch strengthening in nanoscale metallic glasses

The study of structural flaws is of paramount importance in engineering applications. However, the effect of flaws on metallic glasses (MGs) is a debatable topic, drawing from conflicting reports on notch strengthening, notch weakening, and notch insensitivity for MGs. In the present study, molecular dynamics simulations have been performed on notched MGs to systematically investigate the influence of notch geometrical features on their fracture strengths and failure mechanisms. It is found that the symmetric double-edge notched MGs always induce a notch strengthening effect, which becomes more pronounced with increasing notch depth or sharpness. It is reasoned that the constrained growth of the plastic zone is responsible for the notch strengthening behavior. Accompanied by this notch strengthening, the deformation mode shifts from shear banding to homogeneous deformation within the un-notched ligament, when the un-notched ligament length is less than twice the shear band width. Furthermore, our simulations reveal that notch strengthening effect vanishes for asymmetric double-edge notched MGs and single-edge notched MGs. The present study thus provides significant insights into the deformation and failure mechanisms of nano-sized notched MGs, which can be useful in interpreting existing experimental results.