Superplastic bulging capability of Ti-6Al-4V buttcover plate

The investigation on the superplastic bugling capability of 1.5 mm mill annealed Ti-6Al-4V buttcover plate by means of manual gas tungsten arc welding (M-GTAW) and fusion type plasma arc welding (F-PAW) were evaluated respectively. The result shows that untreated Ti-6Al-4V buttcover plate by M-GTAW exhibits no superplasticity, while the same untreated plate by F-PAW, shows good superplastic ability because of extremely fine acicular martensite microstructure of weld metal. To the buttcover plate by M-GTAW, the microstructure of weld metal changed into streaky α structure which exhibits good superplasticity from the original β structure under the condition of the constant temperature of 940°C with the deformation degree of 45%, and changed into the fine equiaxed grain which possesses excellent superplastic ability at the condition of the constant temperature of 800°C with the deformation degree of 40%.