| 7xxx series aluminum alloy is widely used in aircraft truss,wing,tail,etc.because of its high specific strength and good ductility.However,it is difficult to make the 7xxx series aluminum alloy have excellent strong plasticity as well as excellent intergranular corrosion resistance by traditional processing technology.At the same time,the large-scale integral parts exhibit uneven performance at different cooling rates,which limits the life and application potential of the alloy greatly.With 7A04 aluminum alloy in the 7xxx series aluminum alloy as the object of the research,this paper adopts suitable aging system to treat the alloy in the states of water quenching and air cooling,aimed to make 7A04 aluminum alloy match high strength,high toughness,and high corrosion resistance perfectly.This paper analyzes the microstructure and fracture morphology of aluminum alloy by means of metallographic microscope,scanning electron microscope,and transmission electron microscope,and conducts Vickers hardness test,room temperature tensile performance test,and intergranular corrosion performance test on the sample.The effects of different aging systems on microstructure,mechanical properties and intergranular corrosion resistance of 7A04 aluminum alloy were studied.The following conclusions were drawn:(1)Adopted the aging system of natural aging combined with double-stage artificial aging after solution quenching,the tensile strength of water-quenched alloy is 590.7 MPa,the elongation rate is 13.8%,and it has good tensile strength and plasticity.The tensile strength of air-cooled alloy is 477.3 MPa,which is greatly improved compared with T6 aging treatment.This is because the natural aging combined with double-stage artificial aging system provides more nucleation particles for the alloy after air cooling,which lead to more fine and dispersed second phases precipitated after aging.The elongation of the alloy was14.1%,still remaining good plasticity.(2)Compared with T6 aging treatment,using natural aging combined with double-stage artificial aging system,the hardness retention value of alloy air cooling relative to water quenching increased greatly from 56.7% to 66.9%,which shows that natural aging combined with double-stage artificial aging treatment can effectively reduce the non-uniform performance caused by different quenching rates.(3)Compared with T6 aging treatment,the aging system of natural aging combined with double-stage artificial aging improves the intergranular corrosion resistance of the alloy,which is due to the discontinuous distribution formed in the alloy grain boundary prevents the corrosion channels and inhibits the progress of corrosion when using the natural aging combined with double-stage artificial aging. |
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