Ordered B2 phase in a disordered FCC matrix: Current state of research on the development of low-density B2-strengthened Fe-Mn-Al-Ni-C steels

Over the last five years, the automotive industry has primarily focussed on utilising a number of extraordinary properties of B2-strengthened Fe-Mn-Al-Ni-C steels, especially high specific strength, and high strain hardening. While reduction in density may be attributed to the addition of Al, high toughness and strain hardening may be ascribed to the precipitation of non- shearable B2 precipitates which suppresses the formation of shearable L’12-κ-carbides ((Fe, Mn)3AlC carbides). Considering the growing interest in these steels, the present review is aimed at highlighting the present state of research and associated challenges (both fundamental and industrial) with a special emphasis on the influence of B2 precipitate distribution and morphology on the strengthening effect in these steels. In addition, the necessity of obtaining both structural and chemical information about ordered B2 precipitates using the newly emerged methodology of correlative microscopy has also been highlighted.