Shear band propagation and plastic softening of metallic glass under cyclic compression

Shear bands play dominant roles in fatigue damage and fracture of metallic glasses (MGs). In order to explore the effect of cyclic loading on the shear banding behavior, interrupted cyclic compression-compression experiments combined with scanning electron microscope observations using a typical Zr-based MG were performed. With increasing the number of loading cycles, shear bands firstly progressively propagate and eventually stop growing. In contrast to the apparent "work-hardening" behavior caused by the progressive propagation of shear band under monotonic loading, plastic softening occurs and then reaches saturation under cyclic compression. Such cyclic softening behavior is suggested to result from the production of excessive free volume in MGs, which decreases the critical stress for shear band initiation. These findings may improve the understanding on fatigue damage mechanisms and provide instructions for future design of MGs with excellent fatigue performance. (C) 2016 Elsevier B.V. All rights reserved.