Origin of deformation twinning from grain boundary in copper

The occurrence of deformation twinning in face-centered-cubic (fcc) crystals with medium to high stacking fault energy is normally very difficult. Through specially designing the orientation of Cu single crystal, the authors do not only observe profuse nanoscale deformation twins with a tower shape originating from grain boundary but also find some of them terminated in the interior of the grain. The observations clearly prove that the deformation twinning can nucleate through successively emitting partials from grain boundaries, indicating the ubiquity of deformation twinning even in those fcc single crystals deformed at suitable conditions.