Cavitation during superplastic forming of two-phase alloys

Abstract

Many aircraft components are fabricated from superplastic materials such as aluminum and titatium alloys, which exhibit large-deformation characteristics before fracture. Many of them, especially the aluminium alloys, are prone to cavitation under tensile stress, the nucleation and growth of the cavities with deformation leading eventually to premature failure even though the forming conditions remain favourable for superplastic forming. By introducing a nucleation function for cavities, a model is developed to explain the growth of cavities during deformation; good correlation between theory and experiment is observed. The present model tends to over-estimate the cavitation level at large deformation: the discrepancy can be explained in the light of the change in the "equivalent" microstructure of the alloy caused by the presence of large cavities during severe deformation. © 1992.