Mechanical and microstructural analysis on the superplastic deformation behavior of Ti–6Al–4V Alloy

The present investigation has been made to study the superplastic deformation behavior of Ti–6Al–4V alloy based on the theory of inelastic deformation, and to analyze the boundary sliding characteristics using transmission electron microscopy. Flow characteristics for the microstructures of 2.5–16 μm grain sizes were analyzed by the load relaxation tests at various temperatures ranging from 600 to 927°C. The results showed that at relatively low temperatures such as 600°C the grain matrix deformation was dominant and found to be consistent with the state equation based on the dislocation dynamics. On the contrary, above the temperature of 800°C, the grain boundary sliding became dominant resulting in the change of curvature in the stress–strain rate curves, which was more pronounced in the finer microstructures. However, the deformation mode changes from grain boundary sliding to grain matrix deformation with the increase in grain size as evidenced by transmission electron microscopy.