W. Beck, FormTech GmbH, Weyhe, Germany; R. Safiullin, Institute for Metals Superplasticity Problems, Ufa, Russia; R. Imayev, V. Imayev, IMSP, Ufa, Russia

Summary:

Superplastic forming (SPF) of Ti 6-4- and other alloys like eg AA5083 is widely used in aircraft and other industries. The many applications show the variety of the applications, the geometry of parts and process and dies. Very complex shapes are possible. Parts in the thickness range from 0.5mm up to 25mm and max dimensions of up to 4.5m length exist in production. Special advantage is due to comparably low cost in low volume production of parts with a complex shape. For the standard Ti-alloy Ti6-4 the process temperature range is from ~850 to max 940°C. For better process performance, further development is directing towards low temperature forming and increased strain rates. For Ti6-2-4-2 the standard range of process parameters especially has been investigated to define the applicable process window very much in detail with special test device. With help of the data process optimisation for a given application is possible and leads to considerable savings. Unfortunately the existing elevated temperature Ti-alloys like Ti6-2-4-2, beta21S, etc, are not capable to replace Ni-alloys, however. Hot strength and oxydation properties prohibit applications at higher temperatures as ~550°C. Replacement of Ni-alloys for weight reduction in hi-temperature areas, eg. for exhaust systems at the rear end of engines can only be achieved by TiAl-alloys. The forming characteristics of TiAl show very limited elongation however when the “usual” Ti-alloy forming temperatures are applied. Hot tensile tests indicate increased formability only above 1020°C. After modification of the existing SPF press various TiAl sheet metal parts for different test purposes have been formed successfully at temperatures up to 1150°C and gas pressures up to 50 bars. The installed press technology and the elaborated dies can be used for production.