Effect of strain on cavity development during Al–Zn–Mg–Cu alloy superplastic flow

Abstract

Cavitation behaviour has been investigated in an Al–Zn–Mg–Cu alloy with an average grain size of 10 µm during superplastic deformation. The superplastic tensile tests were interrupted at different true strains at 530°C and 3 × 10⁻⁴ s⁻¹. The results showed that cavity nucleation occurred above a critical strain in the optimum loading condition. It was easy for cavities to form at the triple junction due to the stress concentration caused by cooperative grain boundary sliding. Since the tensile stress was higher in the middle of the sample, the cavities were arranged in a straight line parallel to the tensile axis in the centre of the sample. A more appropriate cavity growth equation considering the critical strain was proposed to describe the cavitation behaviour.