Study On Reduction Of Quench Residual Stress In 7050 Aluminium Alloy Die Forgings

For 7050 aluminum alloy die forging,usually go through the solid solution process to meet the requirements of mechanical properties such as strength and toughness.However,the quenching process will also form residual stress in the inner and the surface of the forging.Quenching residual stress of forgings will not only affect the mechanical properties,such as the material static strength,resistance to stress corrosion and fatigue properties,but also affect the size and shape stability in the subsequent machining process.Aiming at 7050 aluminum alloy forgings quenching residual stress formation and cold compression,the stress evolution law in the quenching process and the effects of forgings size on the residual stress were studied by simulation and experimental methods.Analyze the effect and law of cold compression on the quenching residual stress and the material strength.The main research contents are as follows:(1)The residual stress of 7050 aluminum alloy samples with 80×40×10mm at different quenching temperature and quenching residence time were studied.The results show that the residual stress on the surface of the specimen is the maximum compressive stress when the quenching temperature is 20?.When the quenching temperature reaches 60?,the residual stress of the specimen changes from the compressive stress to the tensile stress.When the quencheing temperature is 80?,the residual stress on the surface of the specimen is the maximum tensile stress.The quenching residence time has little effect on the residual stress,and the residual stress is the smallest when the quenching time is 20min.The residual stress of quenching is reduced and measured by cold pressing method,cryogenic method and aging process method.The effect of quenching residual stress on the quenching residual stress is explored,and the cryogenic method and cold pressure are combined.The results show that the effect of cold compression for reducing residual stress is the best,the reduction rate more than 90%.(2)Using Deform finite element software,the stress evolution law of quenching process and the distribution law of quenching residual stress are revealed by simulating the quenching process of 7050 aluminum alloy.The simulation results show that the residual stress on the specimen surface is changed from tensile stress to compressive stress,and its internal residual stress changes from compressive stress to tensile stress.The simulation results show that the reduction effect is more than 90%and it is verified with the experimental results.The difference between them is small,which indicates that the simulation analysis is more reliable.(3)The residual stress of quenching process and the effect of cold pressing process on quenching residual stress reduction were analyzed by finite element numerical simulation for quenching of large 7050 aluminum alloy forgings.The experiment and numerical simulation of 7050 aluminum alloy samples were carried out which is confirmed that the quenching temperature is 40?,the quenching residence time is 20min,and the amount of cold deformation is 3%.