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. (c) 2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.