Synthesis and characterization of multiwall carbon nanotube added Fe-Mn-Al-Si-C low-density steel processed by mechanical alloying and spark plasma sintering

A novel carbon nanotube-added low-density steel, Fe56.75Mn25Al15Si2C0.25 + CNT1, was developed via mechanical alloying followed by spark plasma sintering. X-ray diffraction revealed predominant BCC phases (Fe1.90Mn0.10 and Mn0.90Al1.10) along with minor intermetallics (Fe10Si6 and Mn20C8) after milling and were retained after sintering, further, the phases simulated by CALPHAD are closely aligned with those observed by XRD. Electron microscopy confirmed the successful integration of multiwalled carbon nanotubes into the steel matrix. The Spark plasma sintered sample achieved a density of 5.83 g/cm 3 , significantly lower than conventional steel. Microhardness reached ∼11 GPa with an elastic modulus of 214 GPa and compressive strength is 1134 MPa, indicating superior mechanical performance. The strain hardening exponent n and strength coefficient K are calculated as 0.47 and 3354 MPa respectively.