Mesoscopic examination of cyclic hardening in metallic glass

The deformation behavior of metallic glass (MG) under cyclic nanoindentation tests has been investigated using a meso-scale model, shear transformation zone (STZ) dynamics, which incorporates excess free volume as a state variable. The yield load of MG is found to increase after cyclic indentation in the microplastic regime. The cyclic hardening behaviors are demonstrated to be directly related to the glass structural relaxation reflected by a decrease of excess free volume, which results from the dynamical competition between microplastic events during the cyclic indentation.