Hydrogen trapping at T₁ (Al₂CuLi) precipitates in Al–Cu–Li alloys during aqueous corrosion

The uptake and partitioning of hydrogen during aqueous corrosion in Al–Cu–Li alloys were investigated using focused ion beam (FIB), transmission electron microscopy (TEM), and atom probe tomography (APT). Hydrogen-induced nanopores were observed in FIB-prepared TEM foils from corroded samples but not in uncorroded controls. During corrosion, hydrogen preferentially accumulates at T₁ (Al₂CuLi) precipitates along grain boundaries (GBs) and subsequently forms nanopores under ion irradiation during FIB preparation. With prolonged exposure, nanopores also form at intragranular T₁ precipitates under the same irradiation conditions. APT analysis reveals that T₁ phases exhibit a hydrogen trapping capacity of 3.5 at.%. These precipitates locally deplete solute hydrogen at GBs and impede further hydrogen migration along these boundaries. Our study demonstrates that deliberate design of precipitates as hydrogen traps offers a promising strategy for enhancing the resistance to hydrogen-induced failure in Al–Cu–Li alloys.