A Unified Phenomenological Model for Superplastic Materials 2008-01-1096

Superplastic properties of an aluminum alloy, AA7475 were studied experimentally and simulated by a micromechanically based phenomenological model. The superplastic behavior was studied and predicted at different strain rate and temperature. The model assumes that the total deformation is the result of a composite interaction of grain boundary sliding accommodated by matrix deformation (dislocation climb and glide). Hart's constitutive equations for inelastic deformation of polycrystalline materials are used to represent matrix deformation. The grain boundary sliding is represented through a linear viscous equation originally proposed by Ashby-Verrall. The analysis shows that the Hart's model for high temperature climb processes together with grain boundary sliding can predict the superplastic deformation from the very low to moderately high strain rates.