<p>The work focuses on developing a new low-density steel nanocomposite with a composition of 66.75% Fe 20% Mn 15% Al 2% Si 0.25% C + CNT 1% by weight percent. To synthesize the material, powder of all required elements was mixed, and mechanical alloying (MA) was carried out for up to 50 h. The alloyed powder was consolidated by spark plasma sintering (SPS) at a suitable temperature and pressure, resulting in the development of multiple phases. X-ray diffraction was utilized to characterize and understand the evolution of phases with milling time during the MA process. The phase evolved was BCC (Fe_1.90Mn_0.10, a = 2.86&#xa0;Å, Mn_0.90Al_1.10, a = 3.06&#xa0;Å) along with fewer intermetallic compounds of Fe₁₀Si₆ and Mn₂₀C₈. These multiple BCC phases are retained even after spark plasma sintering with the formation of silicide and carbides. SEM and EDS were employed for microstructural and elemental analysis, respectively. The SPS-treated specimen exhibited a low density of approximately 6.13&#xa0;g/cm³. The low-density effect arises from the combined influence of the lower atomic mass of aluminium and its tendency to expand the lattice parameter in an alloy. The nanoindentation hardness and elastic modulus of the sintered sample were found to be about 9.2&#xa0;GPa and 182.7 GPa, respectively. The improved mechanical characteristics observed in the SPS-treated sample can be attributed to its unique microstructure, which encompasses BCC phases, along with the dispersion of multi-walled carbon nanotubes and nano-sized silicide and carbide precipitates.</p>