Nature Commun. http://doi.org/nrq (2013)

Atomic crystals are far from elastic. Typically, crystals yield inelastically at strains of about 1% because of the activation of dislocations, deformation twinning, cracking, or the appearance of stress-induced phase transformations. However, confinement of the deformation to scales smaller than a few micrometres supresses the basic processes of plastic deformation, which leads to larger elastic strains. In fact, continuous and reversible lattice strains of up to approximately 8% have been probed in defect-free uniaxially loaded micropillars and nanowires, and values exceeding 30% have been predicted for metals. Yet strains above 8% have not been observed in experiments. Now, Evan Ma, Xiadong Han and colleagues report lattice shear strains up to 34.6% (corresponding to a stored elastic energy that is more than 100 times that of bulk metals) in bent Ni nanowires inside a transmission electron microscope. Along the path of applied strain, they observed continuous and reversible phase transformations between various cubic phases, which had been predicted theoretically. The continuous lattice sharing can however be terminated by dislocations at lower strains.