Effect of electric field on cavitation in superplastic aluminum alloy 7475

An externally applied electric field reduced both the volume fraction and the density of cavities which developed during superplastic deformation of aluminum alloy 7475. The decrease in cavitation resulted from a reduction in the nucleation rate of cavities at small strains; their subsequent growth rate was increased by the electric field. The principal nucleation sites for cavities without an electric field were triple junctions of grain boundaries, whereas with an electric field nucleation around second-phase particles also became important. The reduced nucleation rate of cavities in an electric field was attributed to a field-enhanced accommodation of grain boundary sliding. The lower cavitation of aluminum alloy 7475 deformed in an electric field resulted in improved post-deformation strength and ductility.