Microstructure-property-corrosion degradation during 475 °C aging of additively manufactured UNS S32205 duplex stainless steel: experimental and statistical assessment

Duplex stainless steels fabricated by Laser Bed Powder Fusion (LPBF) exhibit refined and metastable microstructures that can be particularly sensitive to intermediate-temperature exposure. In this study, the effect of 475 °C thermal aging on the microstructural stability, mechanical performance, fracture behavior, and corrosion response of LPBF-fabricated UNS S32205 duplex stainless steel is systematically investigated. LPBF specimens were solution annealed and subsequently aged at 475 °C for durations ranging from 100 to 1,000 h, followed by detailed microstructural, mechanical, electrochemical, and fractographic characterization. Microstructural analysis indicates progressive ferrite decomposition during aging, leading to embrittlement and deterioration of mechanical and corrosion performance. These transformations result in significant strengthening at intermediate aging times, followed by strength saturation and a severe reduction in tensile ductility at prolonged exposure. One-way ANOVA confirms that aging induces statistically significant changes (p < 0.001) in young’s modulus, yield strength, ultimate tensile strength, and elongation relative to the solution-annealed condition, while effect size analysis demonstrates that aging duration overwhelmingly governs mechanical variability. Canonical discriminant analysis provides a clear multivariate separation of aging conditions and establishes a direct correlation between the combined evolution of mechanical properties and fracture mode transition from ductile dimple rupture to quasi-cleavage and brittle fracture. Electrochemical testing in 3.5 wt% NaCl reveals a progressive deterioration in corrosion resistance with aging, consistent with chromium partitioning and passive film destabilization associated with ferrite spinodal decomposition. The results demonstrate that LPBF-fabricated UNS S32205 exhibits classical 475 °C embrittlement behavior, with enhanced sensitivity arising from its additively manufactured microstructure. This work provides a statistically validated, process-aware framework linking thermal aging to microstructure-property-corrosion degradation, offering critical guidance for the qualification and reliable deployment of LPBF duplex stainless-steel components in thermally exposed service conditions.