Propagation dynamics of individual shear bands during inhomogeneous flow in a Zr-based bulk metallic glass

In this study, shear-band propagation during serrated and non-serrated flow of a bulk metallic Zr52.2Ti5Cu17.9Ni14.6Al10 (Vit105) glass was investigated. It was found that individual flow serrations can be directly linked to the activation of a single shear band. Rather than reflecting an intrinsic property of the metallic glass, displacement jump magnitudes are shown to be dependent on external factors such as sample and machine compliances. The need to correct experimentally determined displacement jump magnitudes is highlighted, and a solution is presented taking into account the sample–machine assembly. Using these corrected values, an Arrhenius behavior is established on the part of the shear-band propagation velocity of over four orders of magnitude, ranging from 10−2 to 10−6 m s−1 for temperatures between 50 °C and −100 °C. It is shown that the transition from serrated to non-serrated flow can be directly linked to the shear-band propagation velocity, such that the transition occurs at the temperature for which the shear-band velocity equals that of the cross-head velocity applied during the test. Non-serrated flow hence corresponds to a state in which a shear band can be continuously driven at a defined rate in the absence of shear-band arrest.

Research highlights
► Individual load drops occur within a single shear band.
► Shear-band propagation is shown to be a thermally activated process.
► Strain-jump magnitudes are not an intrinsic property of the material.
► Non-serrated flow occurs for applied strain rates exceeding the shear-band velocity.
► Non-serrated flow is not due to kinetic limitations during shear-band nucleation.