Atypical “boomerang” slip traces in [0 0 1] niobium single crystals deformed at room temperature

Niobium single crystals were deformed in compression at room temperature using an homemade device that allows in situ tracking by atomic force microscopy of the surface evolutions at increasing plastic strain. The slip lines exhibit specific structures in the early stage of plasticity consisting of two straight parts lying along well-defined crystallographic directions that are connected by a curved portion. These surface nanostructures are interpreted in terms of elementary plastic mechanisms taking place in the bulk of body-centred cubic materials.