Revealing the intergranular corrosion mechanism of AA5083 alloys through experiments and atomic-scale computation

Continuously exposure to elevated temperature, known as sensitization, can accelerate the precipitation of the electrochemically active ,beta phase (Al3Mg2) at grain boundaries (GBs) in Al-Mg alloys. This results in intergranular corrosion (IGC), which seriously affects the application of Al-Mg alloys in marine environments. Low-angle GBs (<15 degrees) are considered to restrict the nucleation and growth of the ,beta phase, while high-angle GBs (>15 degrees) can promote these processes. However, the quantitative relationship between GB misorientation and IGC sensitivity at atomic scale is unknown. Herein, the underlying mechanism of IGC in AA5083 alloys with ,B phase and GB misorientation is investigated by experiments and simulation. The experimental results show that after sensitization when the misorientation angle exceeded 22.6 degrees, the density of the ,B phase at GBs reaches up to 50 %-60 %. The hybrid molecular dynamics/Monte Carlo algorithm was utilized to simulate the diffusion of Mg and cluster formation in Al-5Mg alloy with 11 different GB models at 300 and 425 K. The maximum GB misorientation angle insensitive to IGC is about 18.9 degrees to 22.6 degrees. However, at 425 K, this angle decreases to 16.3 degrees, increasing the IGC risk of Al-5Mg alloys. The calculation results provide valuable quantitative guidance for the corrosion resistance design of Al-Mg alloys. (c) 2024 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.