Mechanical and microstructural analysis on the superplastic deformation behavior of two-phase Ti-6Al-4V alloy

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 by the use of transmission electron microscopy. The flow curves obtained by load relaxation tests at 600 degrees C and 800 degrees C are fitted well with the inelastic deformation theory. It has been found that the deformation mode for the fine grained microstructures (3 mu m) is a type of iso-stress mode,. while that of coarse grained microstructures (11 mu m) is a mixed type of both iso-stress and iso-strain rate modes. The density of dislocations observed near the grain boundaries is higher along alpha/beta phase boundaries than the alpha/beta grain boundaries, which confirms that the sliding resistance of alpha/beta is lower than that of alpha/beta.