Influence of quenching and aging on residual stress in Al-Zn-Mg-Cu alloy 7449

The present investigation aims to quantify the size and distribution of residual stresses remaining in rectilinear aluminium forged alloy blocks after they had been partially and fully heat treated. Various quench conditions were used, including water at different temperatures and polyoxyethylene glycol in two concentrations. The influence of standard and novel aging procedures, including retrogression and reaging, has been determined. Residual stresses were characterised using X-ray and neutron diffraction. Residual stress magnitudes were found to vary significantly with rapidity of cooling from the solution treatment temperature, with the subsequent aging treatments having a much smaller effect. The influence of heat treatments on the mechanical properties of the alloy was predicted by means of quench factor analysis and measured using indentation hardness and tensile testing. Quench factor analysis is also used to predict the change in lattice parameter arising from different quench paths in the strain free reference samples d(0).