Research About The Effeats Of The Pre-strerching And Aging On The Mierostructure And Mechanical Properties Of7055Aluminum Alloy

7055aluminum alloy is deformable and age-hardenable alloy and has been widely used in aerospace industry due to its high mechanical properties. With the development of the aerospace industry, the demand for7055aluminum alloy with excellent competitive properties increases rapidly. Thermomechanical treatment is a process which can improve the comprehensive machenical properties effectively. In the processes of the industrical manufacture about7055aluminum alloy plate, pre-stretching is always used to reduce the residual stress produced by quenching. The effect of prestretching on microstructure and properties of the alloy after aging is great. But the related study is reported rarely. So it has important theoretical and technical support to improve the properties of the7055aluminum alloy by conducting the research of the effect of the different pre-stretching and the different agings after pre-stretching on the microstructure and properties. Pre-tension deformation can increase the comprehensive mechanical propertiesOn this paper, the effect of different pre-tension deformation,0%-7%, and different aging process such as T6,RRA, T7651and companied by T6, on the microstructure and properties of7055aluminum alloy was investigated by means of hardness test, electrical conductivity test, ambient temperature tensile test, optical microscopy (OM) and scanning electron microscope (SEM). The mechanism was discussed and the main conclusions are as follows:(1) The influence rules of single solid solution on the microstructure and properties of7055aluminum alloy were investigated. The solution of the alloy was more and more fully and the degree of the recrystalization was higher and higher the time extension and temperature raising of the solid solution. Considering the two rules that supersaturation improves the alloy strength and recrystalization reduces it, the optical single solid solution process was determined as470℃/1h.(2) With increasing the pre-stretching, the hardness of the alloy increases to the peak value at3%and then decreases, the ultimate tensile strength firstly decreases to the least value at3%and then increases from3%to4%and decreases at last, the ductility increases from3%to5%and decreases after that. The alloy has the best mechanical properties when it is pre-stretched5%. It is presented a downtrend of the electrical conductivity with the pre-tension increasing, but a little increasing between3%and4%.(3) The effects of the different aging after pre-stretching on the microstructure and the mechanical properties were investigated. With increasing of the degree of over-aging such as T6, RRA and T7651, the size of the second-phase particles increases, which results in the reduction of the hardness, the ultimate tensile strength, the elongation and the electrical conductivity.(4) The effects of the pre-stretching companied by T6aging on the microstructure and mechanical properties were investigated. The ultimate strength and elongation of the alloy after pre-stretching companied by T6aging increases6.7%and20.1%higher than the ones of the alloy treated by T6after pre-stretching respectively. The electrical conductivity is relatively low, which means the alloy have a better capability of stress-corrosion resistance. In a word, the process of pre-stretching companied aging works best for the comprehensive mechanical properties of the alloy.