Deformation twinning in nanocrystalline copper at room temperature and low strain rate

The grain-size effect on deformation twinning in nanocrystalline (NC) copper at room temperature and low strain rate was discussed. It was shown that twinning becomes a major deformation mechanism in NC copper during high-pressure torsion under a very slow strain rate and at room temperature. It was suggested that many twins and stacking faults in NC copper were formed through partial dislocation emissions from grain boundaries. The results show that the Hall-Petch relationship breaks down in NC copper because of the change in deformation mechanism.