Constrained minimal-interface structures in polycrystalline copper with extremely fine grains

Locking in nanoscale strength Metals with nanometer-sized crystal grains are super strong, but they do not generally retain their structure at higher temperatures. This property undermines their high strength and makes their use in applications challenging. Li et al. found a minimum-interface structure in copper with 10-nanometer-sized grains that, when combined with a nanograin crystallographic twinning network, retains high strength to temperatures just below the melting point. This discovery suggests a different path forward for stabilizing nanograined metals. Science , this issue p. 831