Precipitation behavior of κ-carbides and its relationship with mechanical properties of Fe–Mn–Al–C lightweight austenitic steel
P. Chen, F. Zhang, Q.C. Zhang, Jiahui Du, F. Shi, Xiaowu Li
Abstract
The effects of the aging process on the κ-carbide precipitation behavior and thus on the mechanical properties of an Fe-30.5Mn-8Al-1.0C lightweight austenitic steel were experimentally studied. The morphology of intragranular κ-carbide precipitation evolved from spherical to cuboidal and then to rectangular with increasing aging temperature and time, and intergranular κ-carbides precipitate in the high-temperature-aged steels and exhibit lath-like and lamellar morphologies. For steels with intragranular κ-carbide precipitation, the yield strength becomes significantly improved with the persisting aging owing to the enhanced dislocation shearing strengthening via κ-carbide growth, and the increase in yield strength exceeded the contribution of work hardening. Intergranular precipitation in higher-temperature-aged steel has a negative effect on the strength and ductility; it partly counteracts the strength increase due to intragranular precipitation. In summary, the studied steel aged at 550°C for 1–2 h exhibited a better strength–ductility match.