Study on corrosion resistance of artificially aged 7075 aluminium alloy by using Cs-corrected STEM

摘要

This research studied the mechanism of the corrosion resistance enhancement of artificially aged 7075 aluminium alloy using advanced Cs-corrected scanning transmission electron microscopy (STEM). The corrosion behaviors of artificially aged 7075 aluminium alloys in a 3.5 wt.% NaCl solution were investigated by impedance spectra, equivalent circuit analyses, polarization measurements and immersion tests. The results show that a longer aging treatment leads to better corrosion resistance, which can be attributed to the following microstructural features, as revealed by STEM. The Cu segregation at grain boundaries under over-aged conditions helps retard intergranular corrosion. The Mg(Zn,Cu) 2 precipitates formed on the surfaces of Al18Mg3(Cr,Mn) 2 dispersoids effectively insulate the dispersoids as cathodes in corrosion, from the Al matrix. This study demonstrates a potential strategy to design corrosion-resistant alloys achieved by proper alloying and subsequent aging.

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