Observations of Dislocation Structure in AA 7050 by EBSD

Abstract

During and after plastic deformation of metals, dislocations tend to evolve into generally well-defined structures that may include tangles, bands, cell walls, and various additional features. Observation of these structures by electron backscatter diffraction is only accomplished by analysis of changes in orientation from one position to the next. Excess (or geometrically necessary) dislocation densities can be inferred from 2D measurements or obtained directly from 3D measurements as indicated by Nye’s dislocation density tensor. Evolution of excess dislocation densities was measured for a split channel die specimen of aluminum alloy 7050 in the T7451 temper. Densities evolved by a factor or 1.6 for compressive deformations of 15%.