Strain Distribution Across an Individual Shear Band in Real and Simulated Metallic Glasses

Because of the fast dynamics of shear band formation and propagation along with the small size and transient character of the shear transformation zones (STZs), the elementary units of plasticity in metallic glasses, the description of the nanoscale mechanism of shear banding often relies on molecular dynamics (MD) simulations. However, the unrealistic parameters used in the simulations related to time constraints may raise questions about whether quantitative comparison between results from experimental and computational analyses is possible. Here, we have experimentally analyzed the strain field arising across an individual shear band by nanobeam X-ray diffraction and compared the results with the strain characterizing a shear band generated by MD simulations. Despite their largely different spatiotemporal scales, the characteristic features of real and simulated shear bands are strikingly similar: the magnitude of the strain across the shear band is discontinuous in both cases and the direction of the principal strain axes exhibits the same antisymmetric profile. This behavior can be explained by considering the mechanism of STZ activation and percolation at the nanoscale, indicating that the nanoscale effects of shear banding are not limited to the area within the band but they extend well into the surrounding elastic matrix. These findings not only demonstrate the reliability of MD simulations for explaining (also quantitatively) experimental observations of shear banding but also suggest that designed experiments can be used the other way around to verify numerical predictions of the atomic rearrangements occurring within a band.