Load relaxation behavior of ultra-fine grained Ti-6Al-4V alloy

Abstract

In this study, superplastic deformation behavior of ultrafine-grained Ti-6Al-4V alloy was investigated on the basis of the inelastic deformation theory which consists of grain matrix deformation and grain boundary sliding. Specimens with coarse equiaxed grains (11 mu m in diameter) were significantly refined ( approximate to 0.3 mu m in diameter) with high angle boundaries after 4 times of isothermal equal channel angular (ECA) pressing at 600 degrees C. Load relaxation test was performed at 600 similar to 700 degrees C to enlighten the deformation mechanisms operating at specific temperature and to find optimum superplastic forming conditions for ultrafine-grained structures. Main efforts were devoted to analyze quantitatively the relative amount of each deformation mode, i.e., dislocation glide and grain boundary sliding operating at specific temperature.