Methods of eliminating residual stresses in aluminium alloy sheets

In order to meet the needs of production and processing, the residual stresses of aluminium alloy plates need to be eliminated before the next step of production, many imported aluminium alloy sheets are pre-stretched or forged to eliminate most of the internal stresses of the plates, but it is difficult to do so completely, so when doing product processing, there are often slight deformation of the products, which brings a lot of unnecessary troubles for production and processing. In order to solve this problem, today we recommend several methods to eliminate residual stress in aluminium alloy plates.

1. Ageing elimination method

The ageing method is the traditional method of reducing quenching residual stresses. Due to the aluminum alloy plate, especially the aviation aluminum alloy is very sensitive to temperature, the aging temperature increase, must obviously reduce the strength index, so that MgZn2 and other strengthening phase precipitation too much, resulting in over-aging phenomenon. Therefore, post-quenching aging treatment is usually carried out at a lower temperature (less than 200-250°C), thus affecting the stress relief effect (only 10-35%).

2. Mechanical tensioning

The principle of mechanical stretching method is to quench the aluminum alloy plate, along the rolling direction to apply a certain amount of permanent tensile plastic deformation, so that the tensile stress and the original quenching residual stress superimposed on the plastic deformation, so that the residual stress can be eased and released. The results of the study show that the mechanical stretching method can eliminate up to 90% of the residual stresses. However, this method is only suitable for the shape of simple parts, and the uniformity of the aluminum alloy sheet before stretching requirements are high, mostly used in aluminum processing plant.

3. Mould cold pressing method

The mould cold pressing method is used to eliminate residual stresses in complex shaped aluminium alloy forgings by means of strictly controlled limited cold shaping in a specially designed finishing die. In fact the term "die pressing" is inaccurate, because the main mechanism of action is to subject the local material of the aluminium alloy forging to "tension" or "compression".