Structural-weakening mapping to seismic-like slip avalanches in bulk-metallic glasses

Abstract

“Smaller is softer” mainly refers to the reverse size dependence of plasticity for bulk-metallic glasses (BMGs). Here, we report experimental results showing that “flatter acts more ductile”. Specifically, by choosing low aspect ratios for the samples, like 1:2, in compression experiments it is possible to eliminate catastrophically large (system-spanning) slips that are often seen for BMG samples with large aspect ratios of 3:1, 2:1, and 1:1. Moreover, for BMG samples with an aspect ratio of 1:2, multiple parallel shear bands produce self-similar slip avalanches, whose size distribution follows the stress-integrated power-law exponent of around 1.0. This exponent value, agrees with the prediction of mean field theory for a near-zero structural-weakening factor, modeling ductile behavior. The absence of structural weakening for the aspect ratio of 1:2 suggests that this aspect ratio may be preferable for some applications where large slips are undesirable because they lead to jerky deformation behavior and are difficult to control.