Effect of Cryogenic Treatment on Residual Stress and Microstructure of 6061 Aluminum Alloy and Optimization of Parameters

Residual stress induced by solution treatment in 6061 aluminum alloy can lead to workpiece deformation, or even premature failure. The efficiency of traditional heat treatment for relieving residual stress is relatively low. Therefore, this study introduces a novel cryogenic treatment technique to reduce residual stress. The optimal cryogenic process parameters were achieved by orthogonal experiments: cryogenic temperature of 113 K, holding time of 24 h, 1 cryogenic cycle, and a cooling rate of 3 K·min−1, and the residual stress of aluminum alloy was measured by the blind hole method. The microstructural evolutions in 6061 aluminum alloy were tested by OM, SEM, and TEM. The results show that the introduction of cryogenic treatment can reduce residual stress in 6061 aluminum alloy by 64%, mainly due to the reduction of dislocations and the uniform distribution of β’’ phase.