Superplastic Behaviors of a Ti-Alloy with Ultrafine Grain Size

The superplastic deformation behavior of a Ti alloy with submicron grain size was investigated. The ultrafine grained (UFG) Ti alloy exhibits good superplasticity at lower temperature (800°C) and at higher strain rates (not lower than 1.8×10 -2 s -1 ). Severe deformation inhomogeneity(DI) could occur at certain conditions. To lower deformation temperature or to raise strain rate could ease or eliminate inhomogeneity. The influence of deformation conditions and grain size on DI was analyzed. Based on examining on the m value and deformation activation energy of the UFG Ti alloy, SPD mechanisms were proposed to be grain boundary sliding accommodated by dislocation movement at lower temperature and by diffusion at higher temperature.