Influence of stacking fault energy on deformation mechanism and dislocation storage capacity in ultrafine-grained materials

Partial dislocation emission from grain boundaries in metals with medium-to-high stacking fault energies is observed primarily in the grain size range of a few tens of nanometers. Here we report that a reduction in the stacking fault energy permits the emission of partial dislocations from grain boundaries in ultrafine-grained materials with grain sizes significantly larger than 100 nm and this produces twinning. Such twins are effective in increasing the dislocation storage capacity, which may be used to improve the ductility. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.