Research On Quenching Residual Stress And Its Elimination In Large-scale Aluminum Alloy Component

The final heat treatment can increase the mechanical properties of the long chord of 7050 aluminium alloy to a large degree. But the quenching process results in high residual stress in the part. It puts a strain on the size stability and service life on the part. Therefore, it is crucial to control and eliminate these quenching residual stress. In the paper, The influence of different quenching temperature on the properties of the 7050 aluminum alloy was researched, and also measured the thermal expansion coefficient which was needed for the simulation, which provided a reliable material for the numerical analysis model. The quenching simulation model was established, the temperature field and stress field dynamic evolution law of the long chord during quenching were analyzed. The chord material stress state on the surface experienced from tensile to be compressed in the quenching process. While the inner stress state experienced the reverse of that. In the end, leaving high residual compressive stress on its surface. Especially on the surface of rounded corner between the web plate and stiffened plate, the residual compressive stress value was higher, and high tensile stress in its in the core. At the same time, warping and contraction was resulted in the quenching process.Quenching process parameters such as quenching medium temperature, quenching heating temperature, the quenching transfer time influenced on the residual stress were analyzed. The result showed that, the medium temperature had the most impact on the residual stress and distortion. When its temperature increased from 25 ℃ to 80 ℃, the peak stress reduced by about 52%. While quenching temperature increased from 465 ℃ to 495 ℃, the residual stress increased by about 17%. The influence of the quenching transfer time could be ignored. The efficiency of the elimination of chord residual stress under different compression ratio(1.5%, 2.5%, 4%) were compared and analyzed. The residual stress relief both on the surface and in the core was not obvious by 1.5% compression. Increase the ratio to 2.5%, the elimination rate of residual stress was pretty good, reaching 90%. When continue to increase the compression ratio to 4%, the residual stress elimination level hadn’t changed much, but caused new residual stress. So the 2.5% compression ratio was the most appropriate.In order to verify the accuracy of the large chord numerical analysis model. A small specimen of 7050 aluminum alloy was made. The experiment on its quenching and compression was completed. After experiment, the residual stress was tested by XRD. In the end, the quenching and compression simulation of 7050 aluminum alloy specimen identical to simulation parameters used in the chord was conducted. Compared residual stress from simulation with the experimental detection value, the difference was small between them, indicating that the numerical analysis model of the chord was highly reliable.