Cold compression of 7075 and factors influencing stress relief

The residual stresses in heat-treated 7075 aluminum alloy blocks have been characterized using neutron diffraction, X-ray diffraction, and incremental center-hole drilling. Specimens were quenched to induce high-magnitude residual stresses, which were then stress relieved by the controlled application of plastic deformation using a cold compression technique. The experimental variables investigated were the quench water temperature and the postquench delay. This delay is considered to influence the final residual stress magnitudes because of hardening precipitation occurring by natural aging during the period between quenching and the application of plastic deformation. Cold compression significantly lowered the residual stresses in all specimens. Neutron diffraction measurements demonstrated a benefit to applying plastic deformation as soon as possible after quenching. However, this beneficial effect was not evident when characterizing surface residual stresses using hole drilling or X-ray diffraction.