On the variation of the mechanical energy accumulation rates during the flow serrations of a Zr-based bulk metallic glass

Bulk metallic glasses (BMGs) have serrated flows to accommodate plastic deformation at room temperature, where the mechanical energy is accumulated in a stress arising process and then released by a following stress drop. In this study, the variation of the mechanical energy accumulation rate of a Zr-based BMG under varying external disturbances, including the geometric confinement, sample sizes and stress gradients, has been investigated at varying strain rates. In all groups of specimens, the accumulation rates for the elastic strain energy during the plastic-flow serrations are different from the values at the initial elastic stages under compression tests, and have large variations. The variations of the accumulation rates are affected by the applied strain rates, and smaller variations are observed at relatively-lower strain rates (5 x 10(-4) s(-1) and 5 x 10(-5) s(-1)). Such variations in the change of the applied strain rates are independent of the presence of the geometric confinement, size effect and stress gradients, and may be attributed to the intrinsic deformation mechanisms of BMGs. The findings give further insights into the mechanisms on the evolution of flow serrations in BMGs.