Effect of precipitate coherency on the corrosion-induced hydrogen trapping in 2024 aluminum alloy

Abstract

Hydrogen trapping is one of the factors leading to hydrogen embrittlement in heat-treatable high-strength aluminum alloys. The effect of coherency of precipitates on the corrosion-induced hydrogen trapping in aluminum alloy 2024 was investigated by performing artificial aging treatments before corrosion exposure. Two aging temperatures were employed, 170 and 210 °C, for aging times spanning the underaged, peak-aged and overaged conditions. Hydrogen uptake was induced by exfoliation corrosion. Hydrogen evolution from trapping sites was followed by thermal desorption spectroscopy. High resolution transmission electron microscopy combined with geometric phase analysis was performed to analyze the coherency of the precipitates. The results indicated that the coherency state between precipitates and the matrix plays an important role in hydrogen trapping. Hydrogen evolving at 300 °C (T2 state) corresponds to hydrogen trapped by the stress fields of coherent GPB zones and S΄΄ (Al10Cu3Mg3) phases, which form at aging temperatures, below the corresponding solvus temperature. © 2021 Hydrogen Energy Publications LLC