In situ acoustic emission monitoring is shown to capture the initiation of shear bands in metallic glasses. A model picture is inferred from stick-slip flow in granular media such that the origin of acoustic emission is attributed to a mechanism of structural dilatation. By employing a quantitative approach, the critical volume change associated with shear-band initiation in a metallic glass is estimated to be a few percent only. This result agrees with typical values of excess free volume found in the supercooled liquid regime near the glass transition temperature.

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Abstract

Flow serrations recorded during inhomogeneous deformation of Zr52.5Ti5Cu17.9Ni14.6Al10 (Vit105) were studied during compression testing at temperatures between −40 and 60 °C. The shear band velocities determined exhibit a pronounced temperature dependence covering nearly two orders of magnitude. The velocities follow an Arrhenius-type behavior with an associated activation energy of 0.3±0.05 eV. The results demonstrate a thermally activated mechanism of shear band propagation, which is similar to the behavior of other, nonmetallic amorphous materials.