The influence of back pressure on ECAP processed AA 6016: modeling and experiment

A generalized three-dimensional dislocation-density-based two-phase composite model has been further developed to incorporate the effects of hydrostatic pressure during severe plastic deformation. It was applied to equal channel angular pressing of wrought aluminium alloy 6016 with applied back pressure. It was shown that the two-phase composite model approach with additional terms accounting for the presence of hydrostatic pressure is adequate for predicting the cell size of an ultrafine-grained material and also provides a description of the dislocation density evolution. The effect of back pressure is to increase the resultant dislocation density in both the cell walls and the cell interiors. A concomitant increase of the cell wall thickness and cell wall volume fraction and, notably, a decrease in the resultant average cell size was also predicted.