Creep Age Forming Technology And Related Mechanical Properties Of7050Aluminum Alloy Sheets

As an important technology for large integral panels, creep age forming (CAF)has the unique advantages in manufacturing aerospace devices and integral panels ofgiant planes.To improve the forming technology and effectively predict thespringback law during CAF, the creep age forming experiments on artificially aged7050aluminum alloy have been conducted based on theoretical study.Firstly, by orthogonal experiments, the relationships between the maintechnological parameters (age temperature, age time and pre-deformation) andspringback of7050aluminum alloy after CAF were studied, and the involvedinfluences of such parameters were investigated. According to range and varianceanalysis, experimental results show that the factors influencing springback are rangedin such an order, age temperature (T), age time (t) and pre-deformation radius (R).Namely, T has the most important influence on springback,while t and R followed by.Secondly, the variations of the springback of artifically aged7050aluminumalloys in the CAF were characterized by deflection and radius method s. The curve and3D surface plots between springback rate and technological parameters weredeveloped according to experimental response values. The results indicate that there isa little difference between them, but both of the two methods can describe thespringback rate of7050aluminum alloys in the CAF. According to the laws ofspringback rate curves, it is not hard to find that, to a certain range, the higher thetemprature, the longer the time, and the larger the pre-deformation radius, thespringback is much lower after CAF. The3D curve surface can predict the springbackrate ranges effectively on the different conditions.Finally, the mechanical properties of the samples after CAF were tested.Comparative studies on mechanical properties and microstructure between creep ageforming and artificial aging pieces were conducted by scanning electron microscope (SEM), hardness testing and electrical conductivity testing. Based on the experimentalresults, the influences of stress on7050aluminum alloy were discussed. Theexperimental data show that, after age forming processing, strengthening effect ofsamples are not significant. With an age forming temperature higher than180℃,7050aluminum alloy has entered over-aging condition, the tensile strength decreasedobviously. It is necessary to comprehensively consider the springback rate andmechanical properties of the samples, so the best age temperature of7050aluminumalloy is about160℃and the limitation of time should not be longer than15h.Compared with no-stress aging specimen, after age forming, the peak time of tensilestrength and hardness lags, and strength, hardness and electric conductivity of thesamples were higher than no-stress aging test specimen.