Rejuvenation decreases shear band sliding velocity in Pt-based metallic glasses

The lack of plasticity in metallic glasses (MGs) is currently the main drawback limiting their commercialization. Mechanical treatments such as high-pressure torsion (HPT) or cold rolling have successfully improved the plasticity of some MGs. We asked whether we can quantify the change in shear band behavior associated with this enhanced plasticity. To answer this question, we performed numerous nanoindentation measurements on as-cast, annealed and HPT deformed Pt-based BMG samples. We observed different shear band sliding velocities depending on the samples. The amplitude of the velocity peak decreased after HPT deformation and increased after annealing. This study reveals that the decrease in shear band sliding velocity quantifies the degree of rejuvenation in the material after mechanical treatment. The role of the residual stresses on shear band population density is also presented. Thanks to this new approach, it becomes now possible to compare different mechanical treatments, and their ability to rejuvenate a MG.