Effect of aging treatment on microstructure and corrosion resistance of new Al-5.6Zn-1.6Mg-0.15Zr alloy

doi:10.13251/j.issn.0254-6051.2021.01.030

Abstract

Abstract: Changes in the microstructure,corrosion states,and corrosion resistance of Al-5.6Zn-1.6Mg-0.15Zr alloy sheet after aging at 120 ℃ for different time were studied by means of intergranular corrosion experiment (IGC),exfoliation corrosion experiment (EXCO) and electrochemical corrosion experiment,optical microscope (OM),scanning electron microscope (SEM),energy spectrum analysis (EDS) and transmission electron microscope (TEM).The results show that the new Al-5.6Zn-1.6Mg-0.15Zr alloy has good overall corrosion resistance,and its sensitivity to intergranular corrosion and spalling corrosion decreases significantly with the increase of aging time.The polarization curve obtained by electrochemical corrosion experiments also shows the same trend.The effect of aging on corrosion resistance of the alloy is mainly related to the change of grain boundary precipitation phase η (MgZn₂) and the precipitation-free zone (PFZ).With the increase of aging time,the grain boundary precipitation phase aggregates and coarsens,and changes from continuous precipitation to discontinuous precipitation,and the PFZ becomes wider.These changes cause the anodic corrosion channel to be cut off,and the corrosion cannot continue,thereby improves the corrosion resistance of the alloy.

Key words: Al-Zn-Mg-Zr alloy, intergranular corrosion, exfoliation corrosion, microstructure, corrosion resistance

CLC Number:

TG146.2

Huang Yuanchun, Tan Weiyang, Zhang Chuanchao, Wang Yanling. Effect of aging treatment on microstructure and corrosion resistance of new Al-5.6Zn-1.6Mg-0.15Zr alloy[J]. Heat Treatment of Metals, 2021, 46(1): 161-166.

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