Dislocation-density-enhanced passivation of 2205 duplex stainless steel via laser shock peening: first-principles insights

To address the requirement for minimal surface deformation in thin duplex stainless steel (DSS) plates, this study employs millijoule-level laser shock peening (LSP) on 2205 DSS and systematically evaluates its passivation behavior in a 3.5 wt% NaCl solution through a combination of electrochemical testing, time-of-flight secondary ion mass spectrometry (TOF-SIMS), electron backscatter diffraction (EBSD), and density functional theory (DFT) calculations. Previous studies have demonstrated that dislocations can promote the nucleation and growth of passive films, thereby enhancing their integrity and stability; however, the atomic-scale mechanisms underlying this enhancement remain insufficiently understood. The results reveal that the high dislocation density induced by LSP significantly improves the passivation performance. The inner passive layer becomes thicker, while the film exhibits increased enrichment of Mo species. DFT calculations indicate that this enhancement originates from the improved charge carrier transport capability at the metal/passive film interface. Meanwhile, the widening of the passive film band gap leads to a reduction in steady-state passive current density. The strong agreement between theoretical predictions and experimental observations provides compelling atomic-scale evidence for the mechanism by which LSP enhances the passivation behavior of DSS.