When reducing the length scale, a transition from brittle behavior to tensile ductility and homogeneous plastic flow has been observed in nanosized metallic glasses. The sample-size effects have been put forward to explain the suppression of localization and failure of metallic glass wires with dimensions of the order of 100 nm. However, results in disagreement with above hypothesis have been reported, showing that plastic deformation is always size-independent and localized in shear bands. In order to elucidate the contradictory deformation mechanisms we involved molecular dynamics simulations and proved that two characteristics are important for the deformation behavior under tensile load of nanosized metallic glasses: the aspect ratio (length to diameter ratio) and the structure of the nanowire. Hence, a new model is proposed to calculate the critical aspect ratio value at which the brittle-to-ductile transition occurs in metallic glass nanowires. Moreover, by modifying the atomic structure of a brittle nanowire through systematic structural rejuvenation, in terms of creating free volume and disturbing the short-range order, enhanced tensile ductility can be attained.
D. Sopu, A. Foroughi, M. Stoica, and J. Eckert, Nano Lett. (2016)