Research group

Solidification Processes and Complex Structures


Contact person

Dr. Daniel Şopu

Phone: +49 351 4659 878
Email:  d.sopu(at)ifw-dresden.de


Team

Projects

Publications

Devices and techniques

Nanowires


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)

Uniaxial tensile stress−strain curves together with the contour maps showing the atomic volume distribution
relative to the bulk value in the nanowires with the shell (b) and whole volume (c) rejuvenated, respectively, in comparison to the as-cast sample (c). The white circles mark the locations of the FI local motifs within a thin slab of a thickness of 5 nm cut out of the cylindrical nanowires.