| As one of the most significant materials in modern aircraft,aluminum alloy 2024 is a high strength duralumin alloy which can be heat treated,and it is widely applied to the aerospace field due to its excellent mechanical properties.According to the aircraft accidents in the past few decades,although human factor is a main reason for aircraft crash,a considerable number of accidents and failures are caused by structural corrosion damage.The corrosion of aluminum alloy often develops slowly,if it is not dealt with in time,once serious corrosion occurs,it will lead to the decline of aircraft reliability,and even the accident of aircraft destruction and death may occur in serious cases.The corrosion of aluminum alloy2024 is not easy to be detected,and the corrosion degree will increase slowly.In order to reduce the serious flight accidents caused by the corrosion of aluminum alloy,the effect of aging treatment on the corrosion resistance of aluminum alloy 2024 is studied.In this dissertation,the optimal aging treatment is selected based on the different mechanical capacities of aluminum alloy treated by various aging treatment process.Optical microscope and SEM are used to analyze the relationship between microstructure and aging treatment.Effect of aging treatment on corrosion resistance of aluminum alloy 2024 is studied by intergranular corrosion experiment,exfoliation corrosion experiment,uniform corrosion experiment and electrochemical analysis method.As the aluminum alloy 2024 used in aviation needs to undergo severe stress at high altitude,it is necessary to choose appropriate heat treatment process to obtain excellent mechanical properties.Therefore,before the corrosion experiment,the heat treatment is selected first,and the corresponding peak aging treatment,over aging treatment and two-stage aging heat treatment of aluminum alloy 2024 are carried out by orthogonal experiment.After that,hardness and tensile tests are conducted,and the corresponding microstructure and SEM diagrams are compared to analyze the relationship between them.These experiments determine that the peak aging heat treatment of aluminum alloy 2024 is495℃×1h+190℃×10h;and the over aging heat treatment is 495℃×1h+190℃×20h;the two-stage aging heat treatment is 495℃×1h+110℃×2h+180℃×8h.After selecting the heat treatment process,intergranular corrosion experiment,exfoliation corrosion experiment and uniform corrosion experiment are carried out.In the intergranular corrosion and exfoliation corrosion experiments,the corrosion situation of aluminum alloy 2024 is measured by optical microscope.In the uniform corrosion experiment of aluminum alloy,3.5% sodium chloride solution is used to simulate seawater.The corrosion resistance of aluminum alloy 2024 with seawater as corrosion medium is researched with different aging heat treatment.In the intergranular corrosion experiment,the samples exhibit uniform intergranular corrosion and partial point corrosion patterns.In intergranular corrosion test,by measuring the corrosion depth by optical microscope,it can be concluded that the corrosion resistance ranked from strong to weak are natural aging treatment,two-stage aging treatment,peak aging treatment,over aging treatment.In the exfoliation corrosion test,the result can be observed by SEM and optical microscope,the corrosion resistance ranked from strong to weak are natural aging treatment,two-stage aging treatment,over aging treatment,peak aging treatment.In uniform corrosion test,the corrosion rate can be calculated by weighing difference before and after corrosion,the corrosion resistance ranked from strong to weak are natural aging treatment,two-stage aging treatment,peak aging treatment,over aging treatment.Finally,the Tafel curves and EIS of aluminum alloy 2024 with different aging treatment are measured by electrochemical workstation.The aluminum alloy 2024 are tested in 3.5 wt%Na Cl solution.Through analyzing the polarization curve and EIS,the corrosion resistance ranked from strong to weak are natural aging treatment,two-stage aging treatment,peak aging treatment,over aging treatment.Through a series of mechanical and corrosion experiments,in contrast to the natural aging treatment,the peak aging treatment can effectively increase the mechanical capacities of aluminum alloy 2024,but the material plasticity decreases,and the two-stage aging treatment can effectively compensate for the deficiency of plasticity of aluminum alloy 2024 with peak aging treatment;In terms of corrosion resistance,natural aging is superior to artificial aging,and the two-stage aging treatment can effectively improve the corrosion resistance of peak aging treatment. |
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