High strength and ductile low density austenitic FeMnAlC steels: Simplex and alloys strengthened by nanoscale ordered carbides

We introduce the alloy design concepts of high performance austenitic FeMnAlC steels, namely, Simplex and alloys strengthened by nanoscale ordered kappa-carbides. Simplex steels are characterised by an outstanding strain hardening capacity at room temperature. This is attributed to the multiple stage strain hardening behaviour associated to dislocation substructure refinement and subsequent activation of deformation twinning, which leads to a steadily increase of the strain hardening. Al additions higher that 5 wt-% promote the precipitation of nanoscale L'1(2) ordered precipitates (so called kappa-carbides) resulting in high strength (yield stress similar to 1.0 GPa) and ductile (elongation to fracture similar to 30%) steels. Novel insights into dislocation-particle interactions in a Fe-30.5Mn-8.0Al-1.2C (wt-%) steel strengthened by nanoscale kappa-carbides are discussed.