Until 2015, lightweight Fe-Mn-Al-C steels (also known as TRIPLEX steels) with high specific strength (density ~18% lower than that of conventional steels and strength ~1 GPa) were the main centres of attraction in the community of automotive-grade low-density steels . Their microstructures comprised of α-Fe(Al, Mn) based BCC phase and finely dispersed L'12-κ-carbides ((Fe,Mn)3AlCx (x ≤ 1) carbides) in FCC-austenite matrix . However, the primary limitation of these steels was the low strain hardening owing to the precipitation of shearable κ-carbides. Besides, as reported in Ref. , the specific strength of these steels was not comparable to those of Al and Ti alloys. These limitations (of TRIPLEX steels) were addressed by , wherein addition of ~5wt.% Ni to TRIPLEX steels was shown to (i) lead to the formation of non-shearable B2-(Ni,Fe)Al based precipitates and (ii) suppress the precipitation of κ-carbides . This is in contrast to the conventional wisdom of FCC stabilisation by Ni . Besides, addition of C and Mn has also been reported to stabilise the FCC matrix in Ni-added TRIPLEX steels (or, Fe-Mn-Al-Ni-C steels) . In the context of B2-strengthened (B2s) Fe-Mn-Al-Ni-C steels (B2-strengthened Fe-Mn-Al-Ni-C steels will be referred to as B2s Fe-Mn-Al-Ni-C steels, hereafter, in the manuscript), FCC phase provides ductility whereas B2-(Ni,Fe)Al based precipitates account for high strength . In other words, the high overall toughness (total elongation ~20-35% and strength ~1.6 GPa) in B2s Fe-Mn-Al-Ni-C steels may be attributed to an outstanding combination of strength and ductility combination provided by the FCC matrix and B2 precipitates respectively ).