Stress-induced twinning of nanocrystalline hexagonal close-packed titanium in Ti-6Al-4V

Twinning behavior of nanocrystalline hexagonal close-packed titanium in Ti-6Al-4V subjected to severe plastic deformation was investigated. High-resolution transmission electron microscopy observations first showed that the deformation twinning of nanocrystalline hexagonal close-packed titanium was induced. The occurrence of deformation twinning was attributed to the extremely high stress due to specific grain orientations and the large strain rate. The twinning mechanism of nanocrystalline hexagonal close-packed titanium in Ti-6Al-4V was the overlapping of two stacking fault ribbons. This study provided a new thinking that it might be possible to design nanocrystalline titanium and its alloys to extensively activate twinning for further improving their properties.