The long-term reliability of Al–Mg alloys in marine environments is compromised by sensitization-induced precipitation of β-Al 3 Mg 2 along grain boundaries, which leads to intergranular corrosion and mechanical degradation. In this work, a systematic multicomponent microalloying strategy incorporating Mo, Cr, and Ag was applied to an Al–5Mg base alloy to concurrently enhance microstructural stability, mechanical performance, and corrosion resistance under sensitization conditions. Thermodynamic modeling and advanced microstructural characterizations reveal that Mo promotes early formation of Al 18 Mo 2 Mg 3 dispersoids but cannot fully suppress β-phase precipitation. Cr addition refines grains and enhances passive film compactness via Al 12 Mg 2 Cr and Al 45 Cr 7 formation, while Ag introduces high-density nanoscale T-Mg 32 (Al,Ag) 4 precipitates that reinforce grain boundary pinning and reduce galvanic potential variations. The fully alloyed Al–5Mg–0.1Mo–0.1Cr–0.6Ag alloy exhibits a fine-grained structure, high LAGBs fraction, and dense dislocation networks after sensitization. This architecture enables superior performance, retaining high tensile strength (UTS ≈ 378 MPa), enhanced ductility (+20%), and outstanding corrosion resistance (NAMLT mass loss = 7.9 mg·cm -2 ). Electrochemical analyses and DFT simulations confirm that Cr–Ag co-alloying improves passive film stability and increases Al surface binding energy (from 0.6593 eV to 1.0877 eV), indicating enhanced oxide–metal cohesion. This work demonstrates that Cr–Ag-assisted microalloying effectively decouples the strength–corrosion trade-off in non-heat-treatable Al–Mg alloys and offers a robust framework for designing advanced aluminum alloys for marine and high-humidity environments.
Li et al. (Thu,) studied this question.