Atomic-scale characterization of interfaces between 2A70 aluminum alloy matrix and Cu-enriched layer after electropolishing

Abstract The formation of a Cu-enriched layer in Al-Cu alloy upon corrosion has been widely recognized. However, the detailed compositional, structural and interfacial information of this solute enrichment behavior has been ambiguous. Herein, we report on an atomic-scale Cs-corrected scanning transmission electron microscopy (STEM) study on 2A70 aluminum alloy subject to electropolishing, in order to unveil the ambiguities concerning the Cu enrichment. A 2-nm-thick Cu-enriched θ′ phase layer, has been observed underneath the amorphous layer. Three kinds of interfaces between the Al matrix and this layer are observed along different crystalline directions from plane (110), including coherent and semicoherent ones.