Development and characterization of FeMnSi-based shape-memory alloys with austenitic–ferritic duplex microstructure

• Duplex Fe–Mn–Si SMAs were designed by adjusting Si and Cr contents, yielding controlled austenite–ferrite phase fractions. • Duplex microstructures significantly increased yield strength while maintaining comparable recovery stresses to the single-phase alloy. • Higher Cr contents improved corrosion resistance in chloride-containing environments. • Results establish composition–microstructure guidelines for strengthening Fe–Mn–Si SMAs without degrading functional performance. In this study, novel FeMnSi-based shape-memory alloys (SMAs) with austenitic–ferritic duplex microstructures were developed. Based on Thermo-Calc simulations, two alloys with different compositions were produced, characterized using electron backscatter diffraction (EBSD) and energy-dispersive x-ray spectroscopy (EDS) to determine the microstructure of the alloy and the chemical composition of each phase. In addition, thermomechanical experiments were conducted to investigate the effect of the duplex microstructure on the yield stress and recovery stress. It was found that after solutionizing, the FeMnSi-SMAs with a duplex microstructure showed a higher yield stress, a similar recovery stress and lower passive dissolution rate at open circuit potential but a higher sensitivity to pitting at higher potentials in chloride-containing environments compared to the single-phase SMA Fe-17Mn-5Si-10Cr-4Ni 1(V,C), which served as a reference.