Chaotic dynamics in shear-band-mediated plasticity of metallic glasses

The chaotic dynamics describes how a small change of initial conditions can result in a large difference in a deterministic nonlinear system, i.e., the ``butterfly effect.'' Through a combination of experimental and theoretical analysis, here we showed unambiguously that the deformation of metallic glasses (MGs) exhibits such an effect where the experimentally observed plasticity displays a large plasticity fluctuation under the normally same conditions. The ``butterfly effect'' for the plasticity of MGs is related to the chaotic dynamics of a shear band, evidenced by the existence of a torus destroyed phase diagram, a positive Lyapunov exponent, and a fractional Lyapunov dimension. Physically, the chaotic shear-band dynamics arises from the interplay between structural disordering and temperature rise within the shear band, which could lead to an uncertainty in the appearance of the critical condition for runaway shear banding events. Our results provide a perspective on the plasticity of MGs from the viewpoint of complex dynamics and are also important for evaluating the plastic deformation properties of MGs in practical applications.