Enhancing Mechanical and Corrosion Resistance Properties of Fe-25Mn-12Cr-0.3C TWIP Steels via N Alloying and Processing Optimization

High-Mn twinning-induced plasticity (TWIP) steels are renowned for their exceptional strength-ductility synergy. However, their practical applications are severely constrained by inadequate yield strength and poor corrosion resistance. In this study, an N-alloyed TWIP steel (Fe-25Mn-12Cr-0.3C-0.3N, wt.%, designated as TWIP-2) was developed, using an N-free counterpart (Fe-25Mn-12Cr-0.3C, TWIP-1) as a reference. Both steels underwent hot forging (HF) followed by solution treatment (ST). The synergistic effects of N alloying and thermomechanical processing on the microstructural evolution, mechanical properties, and corrosion behavior were systematically investigated. Results indicate that all samples retain a single-phase FCC austenitic structure. N alloying increased the yield strength of the hot-forged TWIP steel from 488.1 MPa to 802.9 MPa while maintaining an elongation after fracture around 40%. Solution treatment markedly improved corrosion resistance, changing the corrosion mode from intergranular attack to pitting. The TWIP-2-ST specimen exhibited the lowest corrosion current density of 2.88 × 10−5 A/cm2 and demonstrated the best overall performance. This comprehensive improvement in mechanical and corrosion performance is primarily attributed to the elevated work-hardening capacity, a higher fraction of low-energy grain boundaries, and the beneficial role of interstitial N in suppressing pitting nucleation and propagation.