Development of Ti–6Al–4V sheet with low temperature superplastic properties

A Ti–6Al–4V alloy sheet with a submicrocrystalline structure (grain size of 0.3 μm) was produced by multistep isothermal forging followed by flat rolling at temperatures below 650°C. The sheet showed a very strong basal texture and isotropic properties in the sheet plane. Room temperature yield strength, ultimate tensile strength, and fatigue limit of the sheet were 1.2–1.3 times higher than that of sheet with micron-sized grains. Sheet with the submicrocrystalline structure showed superplastic properties at temperatures 650–750°C. A complex hollow structure was produced from the sheet by diffusion bonding/superplastic forming at temperatures 750–800°C. The structure had high microstructural homogeneity and high quality of diffusion bonding.