Nanoscale twin boundaries — where one side of the boundary is a mirror image of the other — are not straight as thought, but instead have "kinks". Researchers used a newly developed transmission electron microscopy technique to resolve the orientation of features along these boundaries with 1 nanometer resolution. Twin boundaries that appear straight at lower resolution, actually contain many kink-like steps. These kinks are distributed non-uniformly from twin boundary to twin boundary. By correlating the new results and additional experiments with large-scale simulations, researchers found that these tiny kinks can control how a material deforms when a force is applied. The results also reveal an unexpected mechanism for "de-twinning". These findings demonstrate a need to develop realistic models of nanotwinned structures for designing new high strength materials that exploit the unique properties of twin boundaries.
Defective Twin Boundaries in Nanotwinned Metals