Study On Corrosion Properties Of Aluminum Alloy By Equal Channel Angular Pressing

Equel channel angular pressing technology（ECAP）is more and more widely used in aluminum alloy,commonly used in three typical aluminum alloy 7050,7075,8176 to enhance their strength and hardness.At present,the research on the corrosion resistance of ultrafine aluminum alloy is very limited.Therefore,an experimental study on the Marine and atmospheric corrosion of the three aluminum alloys is carried out in this paper,which will provide strong support for the industrial production and application of ultrafine aluminum alloy.In this paper,electrochemical test and immersion test combined with scanning electron microscopy are used to analyze the corrosion laws of three kinds of aluminum alloys under different extrusion passes at room temperature.It is found that the second phase of 7050 and7075 aluminum alloys is refined after ECAP,and the degree of segregation of the second phase at grain boundary is decreased.The 7050 and 7075 aluminum alloys after ECAP show larger capacitive arc diameter in AC impedance test,larger phase angle and modulus in low frequency band,and lower corrosion rate in corrosion weight loss test.The results show that the corrosion resistance of the two 7 series aluminum alloys is improved after ECAP treatment.After ECAP treatment,the impedance and modulus of 8176 aluminum alloy decrease,and the corrosion rate increases.The corrosion resistance of 8176 aluminum alloy decreases due to the increase of grain boundary volume fraction.In this paper,the electrochemical test and immersion experiment are carried out under the condition of 0℃.It is found that the 7050 aluminum alloy processed by ECAP have a larger impedance,a lower modulus and a lower corrosion rate,indicating that the corrosion resistance is improved.The impedance and modulus of 7075 aluminum alloy specimen increase gradually from 1 to 6 passes,and the corrosion rate decreases gradually,indicating that the corrosion resistance of 7075 aluminum alloy increases gradually.Under the condition of low Cl-diffusion rate,the effect of Al₃Fe and Al₆Fe phase refinement and homogenization is more significant than the increase of grain boundary volume fraction,so the corrosion resistance of 8176 aluminum alloy after extrusion is improved.Compared with the results of AC impedance and corrosion weight loss at room temperature and 0℃,it is found that three aluminum alloys exhibit higher impedance,higher modulus and lower corrosion rate at 0℃.The results of the scanning electron microscopy（SEM）showed that the surface of aluminum alloy in 0℃ environment suffered less corrosion damage and produced less corrosion products.Because the diffusion rate of Cl^-decreased and the corrosion ability weakened,the three aluminum alloys all showed better low temperature corrosion resistance.