Superplastic deformation behavior of Ti-55 alloy without and with 0.1Â wt%H addition

The superplastic deformation behaviors of as-received Ti-55 alloy and hydrogenated alloy with 0.1 wt%H were studied. The results indicate γ hydride readily decomposes and hydrogen easily escapes under vacuum or argon-protected condition near the starting temperature of α + β / β transformation. Compared with as-received alloy, the optimum superplastic temperature of hydrogenated alloy is reduced by about 125 ℃. Larger decrease of elongation in hydrogenated alloy appears if the deformation temperature and initial strain rate deviate from optimal ones. More proportion of β phase distributes uniformly around α phase grain boundaries and prominently inhabits the formation of voids in hydrogenated alloy during superplastic deformation. Hydrogen addition can lead to the improvement of discontinuous dynamic recrystallization mechanism and deformation compatibility of grain boundaries, as well as the reduction of dislocation pile-ups and tangles.