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 mum) was produced by multistep isothermal forging followed by flat rol ling at temperatures below 650 degreesC. The sheet showed a very strong bas al texture and isotropic properties in the sheet plane. Room temperature yi eld strength, ultimate tensile strength, and fatigue limit of the sheet wer e 1.2-1.3 times higher than that of sheet with micron-sized grains. Sheet w ith the submicrocrystalline structure showed superplastic properties at tem peratures 650-750 degreesC. A complex hollow structure was produced from th e sheet by diffusion bonding/superplastic forming at temperatures 750-800 d egreesC. The structure had high microstructural homogeneity and high qualit y of diffusion bonding. (C) 2001 Elsevier Science B.V. All rights reserved.