Abstract
Shear band in metallic crystals is localized deformation with high dislocation density, which is often observed in nanopillar deformation experiments. The shear band dynamics coupled with dislocation activities, however, remains unclear. Here, we investigate the dynamic processes of dislocation and shear band in body-centered cubic (BCC) tungsten nanowires via an integrated approach of in situ nanomechanical testing and atomistic simulation. We find a strong effect of surface orientation on dislocation nucleation in tungsten nanowires, in which {111} surfaces act as favorite sites under high strain. While dislocation activities in a localized region give rise to an initially thin shear band, self-catalyzed stress concentration and dislocation nucleation at shear band interfaces cause a discrete thickening of shear band. Our findings not only advance the current understanding of defect activities and deformation morphology of BCC nanowires, but also shed light on the deformation dynamics in other microscopic crystals where jerky motion of deformation band is observed.
Highlights
Plastic deformation of crystals is controlled by the generation and propagation of lattice defects, most importantly, dislocations
Here we study the deformation of [112]-W nanowires using in situ nanomechanical testing under high-resolution transmission electron microscopy (HRTEM) and atomistic simulations
Our findings indicate that the deformation, discrete thickening and recoverability of the shear band in metallic nanopillars are all controlled by the interface processes, through the interplay of dislocations and local strain concentration near the shear band interfaces
Summary
Plastic deformation of crystals is controlled by the generation and propagation of lattice defects, most importantly, dislocations. An exception was the [112]-orientated nanowire, showing substantial plastic flow via dislocation and shear band activities under both tension and compression. An exception was the [112]-orientated nanowire, showing substantial plastic flow via dislocation and shear band activities under both tension and compression23 Such shear induced deformation bands were frequently observed during the nanocompression of various metallic nanopillars, including both the FCC and BCC www.nature.com/scientificreports/. Metals; yet, the fundamental mechanism regarding shear band dynamics remains largely unknown, especially on how they are coupled with dislocation activities. To clarify these uncertainties, here we study the deformation of [112]-W nanowires using in situ nanomechanical testing under high-resolution transmission electron microscopy (HRTEM) and atomistic simulations. The stress concentration near the border of the shear band causes a preferential dislocation nucleation in this region, leading to discrete thickening of the shear band
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