Mechanical behavior of shear bands and the effect of their relaxation in a rolled amorphous Al-based alloy

Using nanoindentation, atomic force microscopy and high-resolution transmission electron microscopy (HRTEM), the effect of cold rolling and subsequent annealing on the microstructure and mechanical behavior of an amorphous Al–Ni–Y alloy has been investigated. Rolling moderates the serrated flow as compared with the as-spun alloy. Annealing recovers the serrated flow, and the rolled/annealed sample exhibits even more pronounced serrations than the as-spun sample. Rolling reduces the hardness, whereas annealing enhances it substantially. Combining HRTEM with frequency filtering, nanovoids at shear bands in the rolled and rolled/annealed samples were imaged. In the rolled sample, a great number of nanovoids are located in the interior of shear bands. Annealing does not change their distribution. The excess free volume has a more substantial impact on the plastic-deformation resistance of shear bands than do the nanovoids.