Residual Stress Characterization And Relief Methods Of 2A14 Aluminium Alloy Plate

Al-Cu series aluminum alloys are widely applied in aerospace industry because of their high corrosion resistance, excellent mechanical properties and good processability. Aluminum alloys are normally quenched into cold water after solution treatment in order to obtain good mechanical properties. Rapid quenching can lead to the development of residual stress up to the yield point magnitude of the alloy. These residual stresses have a detrimental effect on the performance of materials, such as stress corrosion, fatigue life, dimensional stability. It also leads to distortion during the machining process. Therefore, it is important to reduce the residual stress of aluminum alloys plates that generats during quenching process.The crack compliance and contour methods were studied by using finite element model. The testing process and error factors were systematically analyzed, and then corrected. The quench-induced residual stress of 2A14 aluminum alloy were measured by crack compliance and contour methods. Surface residual stress of the sample was also measured by XRD and ultrasonic methods. The residual stress measured by crack compliance and contour methods were in good agreement with that measured by XRD and ultrasonic methods. The release rule of residual stress when the sample was cut from large dimension plate. In order to keep the residual stress profile of heavy gauge plate, the sample dimension m ust greater than 2.5 times of thicknessThe residual stress evolution during quenching, ageing, and uphill quenching were studied by using ABAQUS software. Hyperbolic sine constitutive equation of as-quenched 2A14 aluminum alloy established by isothermal compression tests was used to model stress-strain relationship during quenching. A Norton creep law established by creep behavior testing was used to model stress-strain relationship in the visco-plastic analysis. HTC calculation was implemented on FEA package Deform-HT. The palstic material constitutive model, creep constitutive equation, HTC were applied to the residual stress simulation process. Residual stress was reduced as the cooling rates decreased during the quenching. During ageing process, residual stress is relaxed as ageing time increased. Higher residual stress reduction can be achieved by using a high temperature uphill quenching medium, or increasing the heat exchange rate between the specimen. Three or four times uphill quenching is the most efficient way to reduce the quench-induced residual stress. More times uphill quenching has no obvious effect on the residual stress reduction. The numerical simulation results are in good agreement with the experimental measurements with around 11.2-15.7% deviation at the largest.In order to improve the balance of mechanical properties and residual stress, residual stress in 2A14 aluminum alloy minimized by modifying the quenching cooling rates, uphill quenching and thermal-cold cycling were investigated in this study. Residual stress as well as the tensile properties, microstructures and dimensional stability of 2A14 aluminum alloy have been investigated systematically. The results showed that the boiling water quenching results in a 91.4% reduction in residual stress magnitudes compared with cold water quenching(20 °C), but the tensile properties of samples quenched in boiling water were unacceptably low. Quenching in 80 °C water results in 73.7% reduction of residual stress, and the reduction of yield strength is 12.7%. The residual stress and yield strength level is considerable for the dimensional stability of aluminum alloy. Quenching samples into 30% polyalkylene glycol quenchants produced 52.2% reduction in the maximum compressive residual stress, the reduction in yield strength is 19.7%. Moreover, the effects of uphill quenching and thermal-cold cycling on the residual stress were also investigated. Uphill quenching and thermal-cold cycling produced approximately 23~40.7% reduction in residual str ess, while the effect on tensile properties is quite slight.The influence of some factors(compressive ratio, friction coefficients between cold die and component, ageing condition of 2A14 aluminum alloy) on the residual stress of quenched component after cold compression were investigated by using ABAQUS software. The greatest residual stress reduction can be achieved by applying 2% cold compression in present study. Lubricated compression conditions should obviously be preferred over dry conditions for efficient residual stress relief. Cold compression process must carry out immediately after quenching. The simulation results were in good agreement with that measured by contour method. In summary, the numerical simulation model of 2A14 aluminum alloy durin g heat treatment process and cold compression are able to predict the quench residual stress with high precision. It can be used to guide and improve the residual stress control processing of actual production.