Deformation mechanisms of nanocrystalline alpha titanium in Ti-6Al-4V

The deformation mechanisms of alpha titanium with the hexagonal close-packed structure in Ti-6Al-4V subjected to severe plastic deformation were investigated. The fine-structure characteristics of alpha titanium with different nanocrystalline sizes were observed and analyzed via high-resolution transmission electron microscopy. The experimental results suggested that dislocation slip was the dominant deformation mechanism and the pyramidal 〈c+a〉-type dislocation slip was liberally activated as the nanocrystalline size was larger than 15 nm. Meanwhile, twinning on {11¯01} plane contributed much less to the deformation. As the nanocrystalline size decreased to be smaller than 15 nm, grain boundary sliding would accommodate the deformation.