Nanotwins induced the formation of passive films and protective oxides: an effective pathway to enhance corrosion resistance in ultra-high strength-ductility nanolayered dual-phase steel

This study focuses on introducing twin structures into the nanolayered structure and deeply explores its influence on the initial corrosion behavior and product evolution of martensite-austenite dual-phase high-strength steel, with emphasis on the role of nanotwins in the corrosion behavior of nanolamellar dual-phase steel. First, we successfully developed a new type of nanolayer twinned martensite-austenite dual-phase (NLT-MADP) high-strength steel. Subsequently, the corrosion behavior of this new steel was studied through potentiodynamic polarization corrosion and salt spray corrosion tests. The research results show that there are high-density nanotwins in the austenite layer of the NLT-MADP high-strength steel. This steel exhibits excellent performance, with the product of yield strength and elongation reaching up to 48.6 GPa%, and the corrosion rate is significantly reduced to 0.19 mm/year. Further analysis of the reasons for its corrosion resistance reveals that the highly active twin boundaries can effectively capture oxidizing substances, thereby increasing the effective nucleation sites of the passivation film. Moreover, the high-density nanolayer interfaces and twin boundaries contribute to the formation of a uniform and dense protective oxide layer, which greatly improves the long-term corrosion resistance of the steel. In conclusion, the strategy of introducing nanotwins into the nanolamellar structure provides a new perspective for the development of new high-performance corrosion-resistant steels.