Influence of structural heterogeneity on shear bands in fracture-affected zones of metallic glasses

Abstract

The catastrophic fracture of metallic glasses (MGs) caused by shear banding limits its engineering application. Structural heterogeneity of MGs strongly affects the shear banding process during plastic deformation. Here, we study the microstructure of MG fibers of different Poisson's ratios or structural heterogeneities after stretching them to fracture using synchrotron X-ray nano-computed tomography with the combination of high-resolution transmission electron microscopy. It is found that interlaminated high- and low-density layers induced by shear banding appear in the fracture-affected zone of the MG fibers. Meanwhile, the fraction of crystal-like order regions in the fracture-affected zone is larger than that of the unaffected matrix. With the increase of Poisson's ratio, the number of low-density shear bands (SBs) increases, and the thickness of a single high-density layer around SBs decreases in fracture-affected zone. The size of fracture-affected zone increases from ∼310 nm for La60Ni15Al25 MG to ∼920 nm for Pd40Cu30Ni10P20 MG. The results help to understand the influence of structural heterogeneity on the plastic deformation of MGs.