Advanced superplastic forming and diffusion bonding of titanium alloy

Abstract This paper reports on investigations of the solid state formability and weldability of Ti–6Al–4V titanium alloy sheet with submicrocrystalline structure (grain size 0·5 and 0·8 μm) under superplastic conditions at temperatures of 700 and 800°C. It has been established that the submicrocrystalline condition of the sheet material reduces the temperature of superplastic forming (SPF) by 200°C and of diffusion bonding (DB) by 100°C, compared to the conventional superplastic forming Ti–6Al–4V material with microcrystalline structure (grain size 3 μm). Unlike commercially available sheet, the submicron grained sheet is characterised by isotropic formability. Submicrocrystalline processed Ti–6Al–4V sheet can be successfully used in SPF/DB technology. The temperature range of superplastic forming can be between 700 and 800°C, and diffusion bonding at 800°C.