Effect of precipitate embryo induced by strain on natural aging and corrosion behavior of 2024 Al alloy

Pre-aging precipitates in 2024 Al alloy re-dissolved during rolling, and Mg and Cu atoms were enriched in the dislocation structure to form "precipitate embryo", which is beneficial for the formation of second phase during the subsequent natural aging process. Due to the solubility of the large precipitate particles during deformation, the precipitates in the natural aging 2024 Al alloy were consist of two parts: The undissolved pre-precipitates and the natural aging precipitates derived from the embryos. The electrochemical corrosion behavior and passive film of the samples with different pre-aging time and strain were investigated by electrochemical tests and SEM. The results showed that the corrosion resistance and the passive film performance were deteriorated with the increase of pre-aging time due to the simultaneous increase of the quantity of the two-parts precipitates. The corrosion resistance can be improved by the increase of strain, because there will be smaller grain size and the existence of large undissolved precipitates in smaller strain samples.