Modification of Residual Stress and Microstructure in Al-Cu-Mg Alloy by Cryogenic Aging Treatment

The residual stresses generated during the solution treatment of large cylindrical aluminum alloy components can impact the dimensional accuracy of structural components and even lead to premature failure of the parts. To reduce the residual stresses generated during the solid solution treatment of aluminum alloys, a new method combining cryogenic control system treatment and oil bath aging was designed. The residual stresses of the specimens were measured using x-ray diffraction and blind hole methods. Changes in the microstructure were observed through scanning electron microscopy and transmission electron microscopy, which revealed the relationship between the dislocation density and the residual stresses of aluminum alloys. The results indicate that this novel treatment method reduced residual stresses by 86%. The reduction in dislocation density and the dispersion of delicate secondary phases through precipitation are the primary intrinsic factors attributed to the reduction of residual stresses in the aluminum alloy through this new treatment method. The finely dispersed second phase helps improve the hardness of the aluminum alloy.