Size effects in twinned nanopillars
F Hammami and Y Kulkarni, JOURNAL OF APPLIED PHYSICS, 116, 033512 (2014).
Nanotwinned structures are becoming increasingly attractive owing to their potential as optimal motifs for strength, ductility, and grain stability in metals. In this work, we use nanopillar compression as a paradigmatic problem to investigate the interplay between size effects associated with the twin spacing and the finite size of the nanopillars by way of molecular dynamics simulations. Our simulations reveal that the aspect ratio plays an important role in governing the weakening or strengthening effect of coherent twin boundaries under uniaxial compression. We find that there exists an optimal aspect ratio for which the yield strength of twinned nanopillars is slightly higher than even single crystal nanopillars. In addition, we observe that twin boundaries facilitate dislocation-starvation as defects glide along twin boundaries and are eliminated at the free surface. (C) 2014 AIP Publishing LLC.
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