The onset of plasticity of a Zr-based bulk metallic glass

The deformation behaviors of a Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk metallic glassy alloy under step-controlled tensile loads have been studied in situ and systematically using scanning electron microscopy and synchrotron X-ray diffraction. A circular hole, as a stress concentrator, was introduced in the middle of the gauge length of the sample to facilitate the creation of shear bands in a controllable way at the edge of the hole in situ imaging and diffraction studies could be carried out at the identical loads in a quasi-steady state manner. Pair distribution function was used to calculate the strains of different atomic coordination shells and the relative change of the bond lengths of different atomic pairs. The combined imaging and diffraction studies revealed that (1) the extension of solvent–solvent (Zr–Zr) atomic pairs under tension causes the nucleation of shear bands, and (2) the compressive stress field around the shear band tip effectively slows down the fast propagation of shear bands.