Deciphering the evolution of mechanical properties and corrosion resistance in RE-modified Al-Cu-Mg alloys during controlled thermal processing

In the present work, the mechanical properties and corrosion resistance of rolled Al-4Cu-0.25Mg alloy (Alloy1), Al-4Cu-0.25Mg-0.1Er alloy (Alloy2) and Al-4Cu-0.25Mg-0.1Y alloy (Alloy3) before and after heat treatment (T4, T5 and T6) were investigated. The addition of Er and Y increased the mechanical properties, resulting from the enhancement of precipitation strengthening because the amount of precipitate increased. The segregation of Er on the precipitates obtained the most precipitates, resulting in the highest mechanical properties in the Alloy2 samples. Heat treatment strongly affected the contributions of dislocation and precipitation strengthening, where these two mechanisms common induced the highest mechanical properties in the T5 samples. In addition, the corrosion resistance significantly increased after the addition of Er and Y because of the uniform distribution of overall potential and the generation of stable corrosion product film containing RE-containing oxides. Due to the densely distributed precipitates, the Alloy2 samples had the most uniform potential distribution and the lowest corrosion susceptibility, leading to the highest corrosion resistance. Compared with the Alloy1-rolling sample, the Alloy2-T5 sample had higher corrosion resistance even though T5 treatment decreased the corrosion resistance to some extent. Thus, the mechanical properties and corrosion resistance of Al-Cu-Mg alloy were simultaneously increased after the addition of Er and T5 treatment. Specifically, an ultimate tensile strength of 344 MPa, a yield strength of 283 MPa, a fracture elongation of 19.8 %, and a corrosion rate of 11.54 μm y −1 were obtained.