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A size limit for softening

Metallurgy
Strength normally increases for metals as the crystal grain size decreases. However, many processes can coarsen grains, with nanograined metals being especially susceptible to coarsening by heating or mechanical loading. Zhou et al. find that copper, silver, and nickel have a critical grain size under which this coarsening no longer seems to occur under mechanical loading. They attribute this behavior to the suppression of one important type of deformation mechanism called grain boundary sliding. This discovery may help stabilize pure nanograined metals for applications.

Phys. Rev. Lett. 122 , 126101 (2019).