Percolation-like transition from nanoscale structural heterogeneities to shear bands in metallic glass detected by static force microscopy

Abstract

Structural heterogeneities of metallic glasses at the nanoscale have been confirmed by many experiments. Some simulations indicate that these structural heterogeneities show a direct correlation with the initiation of shear bands. However, due to the limited experimental conditions, the detailed evolution from nanoscale heterogeneities to shear bands during deformation is still unclear. Here, a tensile platform coupled with in situ static force microscopy is designed to detect the evolution of nanoscale heterogeneous viscoelasticity during deformation in a CuZr metallic glass. We observe that the dominant viscoelastic mode changes from solid-like to liquid-like with increasing tensile strain, which displays the percolation-like character. Meanwhile, the correlation length of structural heterogeneities increases with strain, and the stripe-like shear bands form when the correlation length reaches a critical value. The current findings not only present a clear picture of the evolution of structural heterogeneities with stress but also reveal the microscopic deformation mechanism of amorphous materials.