Effect of crystal orientations and precipitates on the corrosion behavior of the Al-Cu alloy using single crystals

Al-Cu single crystals with different typical orientations (i.e., (001), (101), and (111)) were prepared to investigate the corrosion behavior of the Al-Cu alloy with and without precipitates by scanning electron microscopy (SEM), transmission electron microscopy (TEM), immersion testing in EXCO solution, and electrochemical impedance spectroscopy (EIS). The results showed that the corrosion rates of the alloy with different orientations increased in the order of (111) < (001) < (101) in the solid solution state (without precipitates), while those of the alloy increased in the order of (101 )< (001) < (111) in the aged state (with precipitates). The corrosion resistance of the alloy without precipitates was mainly determined by the atomic density of the crystal plane, and that of the alloy with precipitates was mainly provided by the corrosion product film. After aging, the precipitation of the theta' phase led to anodic dissolution of the nearby matrix and further accelerated the corrosion rates of the alloy. Furthermore, the corrosion pits of the alloy without precipitates showed geometric shapes corresponding to the crystal orientations. The corrosion of the alloy with precipitates propagated in the form of corroded bands, which were parallel to the {001}(Al) plane. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study found that the corrosion rates of Al-Cu alloy are mainly influenced by the atomic density of crystal planes and the corrosion product film. The precipitation of precipitates can lead to anodic dissolution of the nearby matrix, accelerating the corrosion rates of the alloy.