B2-strengthened Fe-Mn-Al-C-Ni steels as a promising environmentally friendly structural material: review and perspectives

Inspired by the high entropy alloy design strategy, Fe-Mn-Al-C-Ni steels are classified as high-specific strength steels (HSSSs) or compositionally complex steels (CCSs) with a mainly austenite matrix. Fe-Mn-Al-C-Ni steels strengthened by (Ni,Al)-rich B2 phase have attracted vast attention due to its outstanding mechanical properties (yield strength up to 1600 MPa) combined with ductility (elongation 15–38%), low density (∼6.6–6.8 g/cm3),satisfactory corrosion and oxidation resistance. Thermomechanical processing, recrystallization and aging processes on the morphology of the NiAl-B2 phase, considering also relevant strengthening mechanisms, are analyzed. Future prospects of industrial application and research directions aimed at achieving an environmentally-friendly steel are indicated.