2, Brown University, Providence, Rhode Island, United States
Metallic nanowires (NWs) have attracted much attention in recent years for a wide range of applications including flexible and stretchable electronics, where their mechanical behaviors are of important relevance. In this talk, we will present our recent work on in-situ transmission electron microscope (TEM) mechanical testing of crystalline metallic NWs, closely integrated with atomistic simulations. Using a unique nanomechanical testing stage based on the MEMS technology, we measure the stress-strain curves while simultaneously observing the microstructural evolutions. We identify dislocation nucleation from free surfaces as the dominant deformation mechanism. For single crystalline NWs, large plastic deformation is observed as a result of coherent twin propagation. In addition, we find that twin boundaries in the NWs play a critical role in the mechanical behaviors. In the case of bitwinned NWs that have a single twin boundary along the nW length direction, we observe a transition of deformation mechanism from localized dislocation slip to delocalized plasticity via an anomalous tensile detwinning mechanism.