Al-Cu-Fe alloys are promising materials due to their combination of high specific strength, heat resistance and relatively low cost. However, their practical application is hampered by insufficient corrosion resistance in aggressive environments. The structure of these alloys, formed during crystallization and subsequent heat treatment, plays a key role in determining their corrosion properties.
The primary structure of Al-Cu-Fe alloys is characterized by a dendritic structure with the release of intermetallic phases, such as Al₂Cu and FeAl₃, along the grain boundaries. These phases, having different electrochemical potentials in relation to the aluminum matrix, create galvanic pairs that promote localized corrosion, in particular pitting.
Heat treatments such as homogenization and ageing have a significant effect on the microstructure and, therefore, on the corrosion resistance of alloys. Homogenization at high temperatures promotes the dissolution of intermetallics and the equalization of the chemical composition, reducing the tendency to galvanic corrosion. Ageing, on the contrary, leads to the release of dispersed particles of strengthening phases, which can either increase or decrease corrosion resistance depending on their composition, size and distribution.
To improve the corrosion resistance of Al-Cu-Fe alloys, various methods of structure modification are used, including alloying with other elements (e.g. manganese, silicon), pressure treatment and application of protective coatings. Alloying allows changing the electrochemical characteristics of phases and the structure of grain boundaries, pressure treatment – to refine the grain and increase the density of the material, and coatings – to isolate the alloy from an aggressive environment. Further research in the field of structure optimization and development of effective methods of corrosion protection is necessary to expand the scope of application of Al-Cu-Fe alloys.
Author: Rafał Babilas, Anna Bajorek, Monika Spilka, Adrian Radoń, Wojciech Łoński
Institute: Department of Materials and Biomaterials Engineering, Silesian University of Technology, ul. Konarskiego 18a, 44-100, Gliwice, Poland, Institute of Physics, University of Silesia in Katowice, 75th Infantry Regiment, 1, 41-500 Chorzow, Poland, Lukasiewicz Research Network – Institute of Non-Ferrous Metals, ul. Sowinskiego 5, 44-100, Gliwice, Poland