An experimental investigation of the superplastic forming behavior of a commercial Al-bronze

Abstract

The superplastic behavior of thermomechanically processed complex commercial Al-bronze (Cu-10A1-4.5Fe-6Ni-2Mn) sheet material has been investigated under biaxial bulge-forming conditions using constant gas pressures at different temperatures. The results of bulge testing were systematically analyzed using m values determined from uniaxial tensile tests on the same sheet. The variations of dome height and thickness were examined relative to forming time. The rate of the change of dome height was observed to be comparable to the corresponding apex strain rate, and both dome height and m value were seen to influence the thickness gradient. It was also demonstrated that the geometry of a dome was not constant during bulge formation. It could be flatter than, equivalent to, or sharper than a spherical shape. The grain size was relatively small (2 to 3 μm) and very stable, and this is likely to be responsible for the large superplastic strains and relatively low levels of cavitation observed for the alloy.