Thermal laser shock peening-induced composite gradient structure for enhanced post-corrosion fatigue of aluminum alloys

Post-corrosion fatigue is a critical challenge for metallic materials in service environments, particularly for ultra-high-strength aluminum alloys (UHSAAs). In humid or corrosive environments, the nanoprecipitates critical to UHSAAs’ strengthening are prone to anodic dissolution, leading to severe degradation of fatigue performance. Here, we report a depth-dependent subgrain-precipitate composite gradient structure, produced via thermal laser shock peening, that effectively breaks the long-standing trade-off between mechanical and corrosion performance in aluminum alloys. Without compromising strength and ductility, this approach achieves a remarkable three orders of magnitude improvement in V-notched post-corrosion fatigue life. This custom-designed composite gradient structure exhibits surface nanoprecipitates with enhanced chemical stability, substantially mitigating corrosion damage. Simultaneously, stable residual compressive stresses combined with subgrain networks synergistically suppress fatigue cracking. The composite gradient structure represents a promising material design for post-corrosion fatigue resistance.