Effect of cerium content on the evolution of microstructure and mechanical properties in Fe-Mn-Al-C low-density steels

Abstract This study aims to determine the optimal cerium (Ce) addition in Fe-5Mn-5Al-0.5C low-density steel by systematically investigating its effects on microstructure and mechanical properties. Experimental alloys with varying Ce contents (0, 0.012, and 0.17 wt%) were prepared and subjected to solution treatment at 900 °C, followed by aging at 650 °C. Detailed microstructural characterization was carried out using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and X-ray diffraction (XRD), along with tensile testing. The results revealed that the addition of trace Ce (0.012 wt%) significantly refined the grains and promoted homogeneous precipitation of κ -carbides, enhancing the dislocation pinning effect and improving the yield strength, ultimate tensile strength, and ductility, with a notable 5.3% increase in the strength-ductility product. However, excessive Ce content (0.17 wt%) caused grain coarsening, suppression of κ -carbide formation, and the development of brittle Ce-Al-O inclusions, which acted as stress concentrators and led to deteriorated mechanical performance. This study highlights the regulatory effect of Ce content on strengthening mechanisms, including grain boundary and precipitation strengthening, offering valuable insights for the design and heat treatment optimization of high-performance lightweight steels.