Abstract:The microstructure evolution and morphologies of Ti-6Al-4V alloy fracture after superplastic tensile testing were investigated by the optical microscope and the scanning electron microscope. The results show that, the ultrafine-grained Ti-6Al-4V alloy displays quasi ductile fracture in room temperature testing, while the ductile dimples-voids gathered type fracture in the superplastic tensile testing. In the same initial strain-rate, the grains dimension and β phase contents increase, and the voids decrease with increasing of the tensile temperature. From 840 °C to 930 °C, the grains still retain in equiaxed state. At the higher temperature (960 °C), the grains are coarsed and exhibit lamellar crystal at some sections. At the same tensile temperature, the grains dimension and β phase contents increase and the voids decrease with decreasing of the initial strain-rate. At elevated temperature (above 960 °C), β phases have good plasticity and low hardness. More β phase contents are favorable to the grain boundary sliding and the voids are difficult to generate.