Effect Of Pre-deformation On The Creep Age Forming Microstructure And Mechanical Properties Of 7075 Aluminum Alloy

With the rapid development of the aviation industry,more and more requirements are put forward for the forming of the integral panel of the aircraft,and the aging forming is an effective method to form the integral panel.The research on the effect of pre-deformation on the properties of age-forming parts is the development and innovation of traditional age-forming process,which has important theoretical significance and practical value.This paper,taking 7075 Aluminum Alloy sheet of T6 state as the research object,studies material non-aging,aging and age-forming of mechanical properties and microstructure morphology under the condition of pre-deformation and pre-deformation with solution treatment and final heat treatment.The results of the study show that:The age forming rebound rate of T6 7075 aluminum alloy will decrease with the increase of pre-deformation.When the pre-deformation amount is 7%,the rebound rate of the sample reaches the minimum,which is 21.02%,with a decrease of 64.88% when the rate is 0.The 7075 aluminum alloy has good formability at this moment.But its strength compared to the samples without aging state will be greatly reduced.By means of transmission electron microscopy,it can be found that the precipitated phase of sample is made of strengthening phase GP zone and ?' phase,grain boundary precipitates fine continuous while precipitate free zone is not obvious,after age forming,most strengthening phase GP zone and ?' phase disappear with the coarse ? phase emerge,the grain boundary distributes discontinuously,GBP size becomes larger,making the strength of the alloy lower than non aged samples.T6 7075 aluminum alloy after solution treatment can improve the mechanical properties.When non-ageing state pre-deformation amount is 2%,elongation rate is as high as 22.33%,with an increase of 31.35% compared with the extension of the parent material.The rebound rate decreases,as pre-deformation increases with the application of the pre-deformation to alloy based on solution treatment and with final age forming,.When the pre-deformation amount is 7%,the rebound rate reaches the minimum,which is 38.30%,and the forming performance of the sample is also very good,and its strength is 20.89% higher than that of the pre-deformation of 7% at the aging state.On the basis of solid solution treatment,cold deformation and artificial aging,by adding pre-aging before cold deformation,the strength of samples has been greatly improved.This is because the pre-aging can provide matrix fine dispersed phase GP zone and a small amount of ? 'phase,and GP zone will provide conditions for the finnally aging strengthening phase nucleation and precipitation.After aging,aging forming,the ? ' phase is spherified.Spheroidized ?' phase of the uniform distribution will improve the mechanical properties of the alloy.With final thermo-mechanical treatment process,7075 Aluminum Alloy age forming rebound rate will also decrease with pre-deformation increase,but the minimum rebound rate is only 62.66% and forming performance decreases compared with the other two processes in general,the pre-deformation is conducive to reducing the age forming rebound rate.