SUPERPLASTIC FLOW AND FAILURE IN A FINE-GRAINED 7475-AL-ALLOY

An elongation of 907% has been achieved in a fine-grained superplastic 7475E Al alloy by deformation at 517 degrees C at a strain rate of 2 x 10(-4) s(-1). Appreciable grain growth was evident only after an elo ngation of 500% was exceeded thereby inducing localization of necking. A considerable amount of dislocation-particle interactions has been o bserved during superplastic deformation. The combined effect of grain growth, localized necking, and dislocation-particle interactions leads to the nucleation and subsequent growth of cavities.