This experiment will determine the influence of second phase precipitation on subsequent post heat treatment cold compression for heat treatable aluminium alloys. Immersion quenching introduces high magnitude residual stresses. These residual stresses are significantly reduced by controlled application of post quench plastic deformation. The objectives of this experiment are to quantify the reduction in residual stresses arising from the application of a known amount of cold compression, how the post quench delay affects the magnitude and distribution of residual stresses and how the residual stresses measured on ENGIN-X compare with those measured by the slitting technique. The post quench delay is the main experimental variable. During this delay the aluminium alloy undergoes precipitation which affects the work hardening behaviour during cold compression.