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Description
Fe–Mn–Al–C lightweight steels offer an attractive combination of low density and high specific strength, where 𝜿-carbide precipitation provides an important strengthening mechanism. In this study, a CALPHAD-guided alloy-design strategy was employed to optimize the composition and aging treatment in order to maximize the probability of fine and intergranular 𝜿-carbide formation and avoid/minimize the coarse, grain boundaries 𝜿-carbide in Fe–Mn–Al–4Ni–C steel system.
Thermo-Calc/PRISMA simulations were performed over a compositional range of 15–25 wt.% Mn, 4–12 wt.% Al, and 0.6–1.6 wt.% C for an aging temperature window of 500–700 °C. The simulations identified Fe–19Mn–10Al–4Ni–1C as the optimum composition and 600 °C for 10,000 s as the most favorable agingcondition for 𝜿-carbide precipitation. Experimental validation was conducted on as-cast, hot-rolled, and cold-rolled conditions, comprising different number of dislocations and grain size. EBSD and XRD analyses revealed that prior thermomechanical processingstrongly influences phase evolution and microstructural development. Hot rolling and cold rolling promoted grain refinement and enhanced the precipitation formation compared with the as-cast condition. The results demonstrate that combining precipitation modelling with microstructural validation provides an efficient approach for the design of 𝜿-carbide-strengthened lightweight steels.