Structure of the Copper-Enriched Layer Introduced by Anodic Oxidation of Copper-Containing Aluminium Alloy

This paper investigates the structure of the copper-enriched layer formed at the alloy/anodic film interface during anodizing of Al-2 wt.% Cu binary alloy using transmission electron microscopy. It was revealed that θ′ phase was formed within the copper-enriched layer. For the copper-enriched layer formed on {1 0 0} aluminum planes, the interface between the aluminum matrix and the θ′ phase within the copper-enriched layer is coherent. For the copper-enriched layer formed on {1 1 0} and {1 1 1} aluminum planes, the interfaces between the aluminum matrix and the θ′ phase within the copper-enriched layer are semi-coherent or incoherent. The interfacial coherency influences the formation of oxygen gas bubbles within the resultant anodic films.