Shear-banding dynamic and self-repair mechanism of CuZr metallic glass subjected to cyclic nanoindentation: Experiment and molecular dynamic simulation

Abstract

Although metallic glasses (MGs) exhibit exceptional mechanical properties, their practical applications are often hindered by operational conditions that induce cyclic stress and strain fluctuations, leading to sudden failure through rapid shear-banding. Combining experimental tests and molecular dynamic (MD) simulations, we find that although cyclic stress induces the accumulation of shear instability and promotes shear bands (SBs) growth, a unique ‘self-repair’ process occurs inside mature SBs evidenced by an obvious decrease in potential energy and increase in stabilized cluster connections. The unique self-repair behavior is elaborated by coupling the STZ-vortex model and medium-range order (MRO) clusters defined by the gradient atom stacking structure, which suggests that rigid solid-like clusters acting as the rotation center activate the inelastic deformation within surrounding atoms. Such shear-banding dynamic reveals that the self-repair event is caused by the transition from liquid-like atoms to opposite solid-like counterparts, which correlates strongly with enhancing face-sharing connections of MRO. These findings advance our understanding of structural evolution and plastic events during cyclic deformation of MGs.