Enhanced mechanical properties and corrosion resistance of 316L stainless steel by pre-forming a gradient nanostructured surface layer and annealing

Stainless steels with high mechanical properties and corrosion resistance are promising structural materials for the next generation of aerospace and some niche industries. In this work, we pre-formed a gradient nanostructured (GNS) surface layer on 316L stainless steel by surface mechanical rolling treatment (SMRT) and subsequently annealed it at 700 degrees C. Tensile tests showed that the strength-ductility synergy was enhanced in the annealed-SMRT sample, while the grain size and hardness in the GNS layer retained rather stable. In addition, a remarkable Cr-enrichment was found in the GNS surface layer after annealing, resulting in a significantly enhanced corrosion resistance. The underlying mechanisms on the microstructure, composition and phases evolutions, as well as their effects on deformation and corrosion behavior, were analyzed in the annealed-SMRT sample. This work provides insights on developing a simple thermomechanical approach to produce stainless steels with enhanced mechanical properties and corrosion resistance. (C) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.