| Creep age-forming (CAF) is a new technology used to manufacture integral wing panels, which combined age-hardening and creep forming into one process.In this paper, creep age-forming process for2524aluminum component has been studied systematically and the variation of the springback and material properties, microstructure of artificially aged2524aluminum alloys in the creep ageing forming are investigated. The results are as follows.l.By comparing two different measurement methods, that is deflection method and radius method of the springback definition, the radius method of experimental value and regression value match better so more suitable to describe springback.2. The factors influencing springback are arranged in such an order: ageing temperature, keeping time, thickness, pre-deformation radius. The law of each and comprehensive effect of factors on creep aging springback and of AA2524is obtained. Further proven experiments have then been carried out, The result shows that the maximum springback deviation between the experimental results and the prediction ones is within9.89%.It has been proved by lots of experiments that there is a linear relationship between the springback and the pre-deformation radius, and between springback and the logarithm of keeping time(lnt) as well, there is a linear relationship between the springback and the index of ageing temperature, and between springback and the thickness as well.3.keeping the maximum bending stress the same, that is to say, keeping the same relative radius(R0/H) at the upper and lower workpiece surface by changing workpiece’s thickness and pre-deformation radius, the springback is increas with the thickness becoming bigger. That’s to say springback is not only with stress level and stress gradient.4. It is found that the rolling direction springback of double curvature age forming is smaller than single curvature when the ageing temperature, keeping time, thickness are fixed. Based on the same pre-deformation radius, the average is lessened by11.5%.5. By mechanical properties tests of different process after CAF, it is demonstrates that:With the increasing of aging time, the strength and hardness of aluminum work-piece also increase,such as,at160℃,the ageing time increased from0to8hour,tensile strength,yield strengthand handress incressed from423.7,265.3MPa and128.5HV to479.7、348.9and143.1HV however, elongation dropped from17.8to12.3.When reaches a peak value after a certain time(13h), it turns into over-aged state and then decreases with aging time, meanwhile, the elongation decreases with prolonged aging time. So it can be concluded that raising the aging temperature appropriately will speed up the aging process, and shorten the time to reach its peak age hardening condition.6.Owing to different pre-bending stress, the mechanical properties and microstructures of the corresponding parts (tensile and compressive stress part) of the work-piece after CAF, are investigated. Tensile strength, yield strength and Vickers hardness on the compressive side are greater than that on the tensile side, the elongation gradually reduced from compressive side to tensile side. Microstructure analyses show that the main strengthen precipitate of2524alloy plate is S’phase, the precipitate after age forming was long strip shape. Compressive stress (rather than tensile stress) can further promote the precipitate S’increase so that the compression side of the strength is greater than the tensile side. |
PDF Full Text Request