Irreversible rearrangements and fertile regions in deformed metallic glasses

The present study is based on the use of numerical methods to simulate the response of model Ni–Zr metallic glasses to shear deformation. Individual atoms were artificially displaced one at a time to perturb local atomic arrangements. In various cases, the artificial atomic displacements induced a local irreversible rearrangement of the positions of small groups of atoms. The minimum displacement length activating the rearrangement provides a measure of the relative mechanical stability of the group of atoms against deformation. It is shown that the metallic glasses include regions characterized by particularly high degrees of mechanical instability, and then more prone than others to deformation-induced rearrangements. These fertile regions are present in undeformed metallic glasses as a consequence of the quenching process. The shear deformation induces a gradual decrease of their mechanical stability and finally their rearrangement. At the same time, deformation also promotes the formation of new fertile regions. Whereas quenching results in fertile regions uniformly distributed in the metallic glass volume, the fertile regions formed by deformation tend to concentrate in the central portion of the simulated system.