Optimization of Cryogenic Treatment Parameters for the Minimum Residual Stress

Residual stress developed after the quenching of aluminum alloys causes distortion during subsequent machining. The purpose of this study was to reduce the residual stress and improve mechanical properties by using a novel cryogenic treatment in an aluminum alloy, specifically, grade 2A12. The orthogonal test and relevant range analysis method were used to optimize cryogenic treatment parameters for improved distribution of residual stress in 2A12 alloy samples. The changes of microstructure were examined by scanning electron microscopy and transmission electron microscope. It was found that the residual stress in 2A12 alloy could be reduced up to 93%, by optimizing the cryogenic treatment parameters, and the reduction was mainly from grain refinement and uniformly distributed S' precipitates ascribing to the cryogenic treatment. The S' precipitates (Al 2 CuMg) were linked to the formation of Cu-Mg co-clusters, which were broadly equiaxed with no internal order.