Effect of aging treatment on the corrosion performance of Al-Zn-Mg alloys with different grain structures
The effects of aging treatment and grain structure on the corrosion performance of the alloy were investigated by using the medium-strength Al-Zn-Mg alloy as the research object,and using intergranular corrosion,electrochemical polarization curve test,and slow strain rate tensile tests,combined with OM,TEM,SEM,and EBSD observations,respectively.The results show that the corrosion resistance of the recrystallized grain alloy gradually improves with the extension of the double-stage aging time,the intergranular corrosion grade decreases from grade 4 to grade 2,the electrochemical corrosion current density decreases from 27.71 μA/cm2 to 0.098 μA/cm2,and the stress corrosion sensitivity factor decreases from 79.15 to 18.40 when the treatment method changes from the under-aging treatment to the over-aging treatment.The corrosion resistance of the fiber grain alloy is significantly improved compared with that of the recrystallized grain alloy at the same aging stage,including a 35.9%reduction in the maximum depth of intergranular corrosion,an 81.4%reduction in the electrochemical corrosion current density,an 81.9%reduction in the annual corrosion rate,and a 46.2%reduction in the stress corrosion sensitivity index.The improvement in corrosion performance is mainly due to the lower recrystallization fraction and lower percentage of large-angle grain boundary of the medium-strength Al-Zn-Mg alloy.
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