Internal variable approach to microstructural change in 7475 alumin-ium alloy during superplastic deformation

Abstract

Flow behaviour and microstructural changes in fine grained 7475 Al during superplastic deformation have been investigated. A series of mechanical tests and transmission electron micrography has been conducted at various temperatures ranging from 430 to 516degreesC. Quantitative constitutive parameters have been determined from load relaxation tests by applying the internal variable theory of structural superplasticity proposed recently. The validity of the mechanical analysis is proved by the evolution of the microstructure (precipitate free zones PFZs) during the accommodation process. Additional information about the mechanism of PFZ formation was determined by microchemical analysis.