Effect Of Strong Plastic Deformation With Ageing Treatment On The Corrosion Performance Of 7A52 Aluminium Alloy

Al-Zn-Mg alloy is widely used in fuselage structure,armored tanks and rail transit because of its high specific strength.However,with the increase of alloying degree,the resistance to local corrosion is weakened,such as pitting corrosion,intergranular corrosion,exfoliation corrosion and stress corrosion.It is difficult to obtain high strength,high plasticity and good corrosion resistance of Al-Zn-Mg alloy by traditional processing technology.Therefore,this paper takes 7A52 aluminum alloy as the research object,and the alloy is processed by multi-directional forging and aging treatment,so that it has high strength,good elongation and high corrosion resistance.In this study,7A52 aluminum alloy was processed by multi-directional forging and aging treatment,and the mechanical properties and corrosion resistance of the experimental materials were tested.The microstructure evolution and corrosion morphology were observed and analyzed by optical microscope（OM）,scanning electron microscope（SEM）,transmission electron microscope（TEM）and X-ray diffractometer,and the effects of multi-directional forging and aging treatment on the mechanical properties and corrosion resistance of 7A52 aluminum alloy were discussed.The main test results are as follows:（1）After multi-directional forging and aging treatment,the hardness and strength of 7A52 aluminum alloy are greatly improved,and it still has excellent elongation.Its hardness,strength and elongation are 172.4 HV,560.6 MPa and12.3%respectively.（2）After multi-directional forging and aging treatment,the electrical conductivity of 7A52 aluminum alloy increased,and its electrical conductivity reached 34.1%IACS,indicating that its stress corrosion sensitivity decreased.The electrochemical test results show that the passivation ability of the sample surface is enhanced,the corrosion rate is slowed down,and the corrosion tendency is reduced.The corrosion current,corrosion potential and polarization resistance are 5.714×10^-7A,-0.886V and 22633.2Ω,respectively.The test results of intergranular corrosion and exfoliation corrosion show that the intergranular corrosion resistance and exfoliation corrosion resistance of the sample are improved,and the maximum intergranular corrosion depth is 52.08μm,and the exfoliation corrosion grade is PB after 48 hours of corrosion.（3）After multi-directional forging and aging treatment,the grain size of7A52 aluminum alloy is obviously refined,the dislocation density is increased,the precipitation phase in the grain grows slightly and the precipitation phase at the grain boundary is discontinuous.These changes in microstructure are the main reasons for the improvement of mechanical properties and corrosion resistance of 7A52 aluminum alloy.