Formation of large scaled zero-strain deformation twins in coarse-grained copper

Most deformation twins in nanocrystalline metals were reported to produce zero macroscopic strain via either random activation of partials or cooperative slip of three partials. In their coarse-grained counterparts, deformation twins produce a net macroscopic strain and change the grain shape since a twin forms via the glide of a single twinning partial dislocation on successive {111} planes driven by Peach-Koehler force. Here, we report the formation of large scaled zero-macrostrain deformation twins in coarse-grained copper with medium stacking fault energy. The responsible formation mechanism is proposed and its effect on twinning or detwinning processes is discussed. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.