Localized heating during serrated plastic flow in bulk metallic glasses

We have studied the serrated plastic flow observed in Zr40Ti14Ni10Cu12Be24 and Pd40Ni40P20 bulk metallic glass alloys tested in uniaxial compression. Quantitative measurements with sufficient temporal resolution to record the fine-scale structure of the data are reported. These data are used to predict temperature increases in single shear bands due to local adiabatic heating caused by the work done on the sample during plastic deformation. Since the predicted temperature increases are on the order of only a few degrees Kelvin, it seems unlikely that localized heating is the primary cause of flow localization. Instead, changes in viscosity associated with increased free volume in the shear band seem more consistent with experiment. Substantial shear band heating is, however, predicted for final failure, as corroborated by evidence of melting on the fracture surface.