Superplastic characteristics and diffusion bonding of Ti-6Al-4V alloy

It is known that Ti-6Al-4V alloy is one of the excellent candidates for aerospace structure due to their high specific strength. However, its higher cost and low formability relative to other materials tend to limit the wide usage of the material. The purpose of this study is to characterize the superplasticity of this alloy so to obtain materials and process parameters for superplastic forming and diffusion bonding for industrial application. High temperature tensile tests was carried out at the strain rate range of 10(-4) to 10(-2) s(-1) and temperature range of 1123 degrees C to 1223 degrees C. According to the results of the experiment, the optimum diffusion bonding condition was obtained at 1148 degrees C, applying pressure of 4MPa for I hour in argon gas environment, which condition is more practical than expensive vacuum condition. It is shown that at the optimum condition for diffusion bonding with parent metal, the oxide film becomes unstable and the oxygen is diffused into the bulk. At this condition, the mechanical and microstructural integrity at the bonding interface was observed in a sandwich structure and a heavy block of titanium part from massive diffusion bonding process.