Enhanced Stress Corrosion Cracking Resistance in AA7075 by Laser Shock Peening: A Comparative Study of As‐Cast and T6‐Tempers

This study investigates the effect of laser shock peening (LSP) on the stress corrosion cracking (SCC) resistance of as‐cast and T6‐treated AA7075 alloys. Microstructural evolution was characterized using CLSM, TEM, and SEM, while residual stress was measured via X‐ray diffraction. SCC performance was evaluated through electrochemical tests and slow‐strain‐rate tensile testing. Results show that LSP significantly increases dislocation density and introduces high compressive residual stresses in both alloy conditions. However, grain refinement mechanisms differ: dislocation‐mediated refinement occurs in the T6 alloy, whereas coarse second‐phase particles in the as‐cast alloy hinder dislocation motion, limiting refinement. Consequently, LSP‐7075‐T6 exhibits accelerated repassivation, reduced corrosion rate, and a 42% decrease in SCC susceptibility, compared to only an 18% reduction in the as‐cast condition. These findings indicate that compressive residual stress plays a dominant role in inhibiting SCC, while the synergistic effect of microstructural refinement is only fully realized when a favorable initial microstructure enables effective grain refinement.