Methods of enhancing superplastic formability of aluminum alloys by alleviating cavitation

Claim 1

Improvements in a method of superplastically forming a component by deformation comprising the steps of: providing a blank of material having superplastic characteristics to be deformed into the component; providing a die having a cavity surface which is complementary to the shape of the component, and having fluid ports; providing a die opposing cover having fluid ports; providing a fluid supply for introducing fluid under pressure controllably through said fluid ports of said die and said cover; positioning said blank between said die and said cover; bringing said blank to a temperature at which said blank exhibits superplastic characteristics; applying to the blank a first fluid pressure on the cavity side thereof; and simultaneously applying to said blank a second fluid pressure to the cover side thereof; the improvement comprising controlling said first and second fluid pressures as applied to said blank during a forming cycle to generate opposing forces to apply initially a very low or substantially nil pressure differential causing compressive force to opposing sides of said blank and then to reduce the cavity side pressure to permit said blank to be forced toward engagement with said die, and thereafter varying said cavity side pressure as a function of time while maintaining constant the cover side pressure in order to create a net differential pressure in accordance with the predetermined pressure-time requirements as necessary to form the blank into the said component shape, and reducing said pressures at substantially the same rate or reducing said cavity side pressure at a rate slightly lower than the rate of decrease of the cover side pressure whereby the differential pressure reduces gradually until said pressures are eliminated and said blank is caused to fully engage said die.