Effects of aging time on the microstructure and mechanical properties of Fe–Mn–Al–C–Nb lightweight steel

Abstract

In this study, the influence of aging time on the microstructure and mechanical properties of Fe–28Mn–10Al–C–0.5Nb lightweight steel was systematically investigated using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and tensile testing techniques. The results demonstrate that with increasing aging time, the austenite grain size progressively increases, which significantly promotes the precipitation of κ-carbides. Owing to the high thermodynamic stability of NbC, the extension of aging time does not significantly influence the size of NbC particles. The tensile strength and yield strength of the tested steel gradually increase with increasing aging time, whereas ductility remains relatively stable without obvious variation. The steel aged at 550 °C for 4 h has an optimal combination of strength and toughness, with a tensile strength of 1249 MPa, an elongation of 34%, and a strength–ductility product (PSE) reaching 42.46%. During room temperature tensile deformation, the Fe–Mn–Al–C–Nb low-density steel demonstrates a microband-induced plasticity (MBIP) mechanism within the dislocation plane slip system.