Effect of pinning on shear banding in metallic glasses

Unveiling the ingredients that can operate shear bands is a cardinal task to tailor the mechanical properties of metallic glasses. Yet the effect of heterogeneous inclusions on shear banding is still poorly understood. Here, we perform molecular dynamics simulations of the shear deformation of CuZr metallic glasses with a portion of atoms pinned. We find a brittle-to-ductile yielding transition upon pinning, with the critical point where the alloy is the most unstable to the brittle failure shifting to large strains. In the brittle regime the shear band width increases first, then shrinks with the pinning concentration. This is interpreted as the perturbation of the aggregated events in the shear bands: the pinning causes a transition from the dilution of shear bands to the constraint, characterized by a nonmonotonic evolution of the nonaffine correlation length. The nonmonotonicity suggests an optimal microalloying addition to enhance the plasticity. This finding is significant for understanding the mechanism of tuning the mechanical performance of metallic glasses with foreign inclusions.