Orientation dependence of deformation twinning in Cu single crystals

Cu single crystals were subjected to dynamic compression plastic deformation to investigate orientation-dependent twinning. The experimental results showed that twinning is closely related to the ratio of the maximum Schmid factor for twinning partial (mT) to the maximum Schmid factor for perfect dislocation (mS), i.e., mT/mS, rather than mT. The twin volume fraction VT increases with the mT/mS value and the most favorable orientation for twinning has the maximum mT/mS value (1.15). The relationships of mT/mS with both effective stacking fault energy γeff and threshold stress for twinning τT were established for understanding orientation-dependent twinning. Further insights into the orientation-dependent twinning and guidance for developing bulk high density nanotwinned materials are provided.