High Reversible Strain in Nanotwinned Metals

Development of bulk metals exhibiting large reversible strain is of great interest, owing to their potential applications in flexible electronic devices. Bulk metals with nanometer-scale twins have demonstrated high strength, good ductility, and promising electrical conductivity. Here, ultrahigh reversible strain as high as ∼7.8% was observed in bent twin lamellae with 1-2 nm thickness in nanotwinned metals, where the maximum reversible strain increases with the reduction in twin lamella thickness. This high reversible strain is attributed to the suppression of dislocation nucleation, including both hard mode dislocations in the bent twin lamellae, while soft mode dislocations along twin boundaries have insignificant contribution. In situ transmission electron microscopy experiments show that higher recoverability was achieved in twinned Au nanorods compared with twin-free ones with similar aspect ratios and diameters during bending deformation, which demonstrates that the introduction of thin twin lamellae also significantly improves the shape recoverability of Au nanorods. This result introduces a novel pathway for developing bulk metals with the capability for large reversible strain.