Aging elimination is a traditional method to reduce quenching residual stress. Because aluminum alloy materials, especially aviation aluminum alloy materials, are very sensitive to temperature, the increase of aging temperature will inevitably reduce the strength index significantly, which will lead to excessive precipitation of strengthening phases such as MgZn2 and lead to over-aging. Therefore, the aging treatment after quenching is usually carried out at a lower temperature (below 200-250℃), which affects the stress relief effect (only 10-35%).
2. Mechanical stretching method
The principle of relieving stress by mechanical stretching method is to apply a certain amount of permanent tensile plastic deformation to the quenched aluminum alloy plate along the rolling direction, so that the tensile stress is superimposed with the original quenching residual stress and plastic deformation occurs, thus relieving and releasing the residual stress. Relevant research results show that mechanical stretching method can eliminate more than 90% residual stress at the highest. However, this method is only suitable for parts with simple shapes, and requires high structural uniformity of aluminum alloy plates before stretching, so it is mostly used in aluminum processing plants.
3. Die cold pressing method
Die cold pressing method is to eliminate the residual stress in aluminum alloy die forgings with complex shapes through strictly controlled finite cold forming in special finishing dies. In fact, the term "die pressing" is not accurate enough, because its main mechanism is that the local material of aluminum alloy die forgings is "stretched" or "compressed". When the finishing die is pressed down, the finishing punch is embedded in the draft angle of the end face and edge (rib) of the aluminum alloy die forging, which actually "stretches" the web part of the die forging. Therefore, this method is to adjust rather than eliminate the overall stress level of parts, which can release the residual stress in some parts of aluminum alloy die forgings and may increase the residual stress in other parts.