Substructure and dispersion hardening in aged, cold worked, and annealed Al-4 wt pct Cu alloy

Abstract

Electron microscopy and X-ray line profile analyses have been employed to define the microstructures and substructures of pure aluminum and an overaged Al-4 wt pct Cu alloy after various thermomechanical treatments. Tensile tests were performed on the same materials, and the results have been interpreted in terms of structure. A given cold rolling reduction of the aged Al-4 wt pct Cu alloy produced a much higher dislocation density and a less cellular substructure than the same treatment produced in pure aluminum of comparable initial grain size. Annealing after cold work produced similar responses in both the pure metal and the alloy. For the aged alloy in the as-rolled, or rolled-and-annealed condition, dispersion strengthening and substructure strengthening were found to be linearly additive, and they accounted for virtually all the observed tensile yield strength. Substructure strengthening has been discussed in terms of the relation between dislocation density and the spacing and nature of the substructure boundaries.