Abrupt elastic to plastic transition in pentagonal nanowires under bending

In this study, pentagonal Ag and Au nanowires (NWs) were bent in cantilever beam configuration inside a scanning electron microscope. We demonstrated unusual abrupt elastic-to-plastic transition, observed as sudden change of the NW profile from smooth arc-shaped to angled knee-like during the bending in the narrow range of bending angles. In contrast to behavior of NW in tensile and three-point bending test, where extensive elastic deformation was followed by brittle fracture, in our case after the abrupt plastic event NW was still far from fracture and enabled further bending without breaking. Moreover, we found that if NWs are coated with alumina, abrupt plastic event is not observed and NWs can withstand severe deformation in elastic regime without fracture. Mechanical durability under high and inhomogeneous strain fields is an important aspect of exploiting of Ag and Au NWs in applications like waveguiding or conductive network in flexible polymer composite materials.