Pseudoelasticity and Shape Memory in Metal Nanowires

Novel shape memory effect (SME) and pseudoelastic behavior are discovered in single-crystalline Au, Cu, and Ni nanowires with lateral dimensions of 1.5-10 nm. Under tensile loading and unloading, these wires can recover elongations of up to 50%, well beyond the recoverable strains of 5-8% typical for most bulk shape memory alloys (SMAs). Results of atomistic simulations and evidences from experiments show that this phenomenon only exists at the nanometer scale and is associated with a reversible crystallographic lattice reorientation driven bythe high surface-stress-induced internal stresses at the nanoscale.This understanding also explains why these metals do not show an SME at macroscopic scales.