Study of the intrinsic ductile to brittle transition mechanism of metallic glasses

We provide a quantitative account of the shear-banding behavior in Mg-based bulk metallic glasses. Microcompression experiments showed that shear bands propagated in an intermittent manner at the micron and submicron scales. The shear-banding kinetics involves competition between shear-induced softening and subsequent recovery mechanisms; the former depends strongly on the elastic energy release rate at the onset of shear-banding, whereas the latter is correlated with the shear-band offset and scales with the characteristic dimension of the microsamples. With the increase in the sample size, more elastic energy is released into the shear band, which results in larger fluctuations in the serrated plastic flows and the propensity for unstable shear-band propagation. The outcome of the current study reveals the origin of the intrinsic ductile to brittle transition mechanism in metallic glasses. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.