Precipitation behavior of k-carbides and its relationship with mechanical properties of Fe-Mn-Al-C lightweight austenitic steel

The effects of the aging process on the kappa-carbide precipitation behavior and thus on the mechanical properties of an Fe-30.5Mn-8Al-1.0C lightweight austenitic steel were exper-imentally studied. The morphology of intragranular kappa-carbide precipitation evolved from spherical to cuboidal and then to rectangular with increasing aging temperature and time, and intergranular kappa-carbides precipitate in the high-temperature-aged steels and exhibit lath-like and lamellar morphologies. For steels with intragranular kappa-carbide precipitation, the yield strength becomes significantly improved with the persisting aging owing to the enhanced dislocation shearing strengthening via kappa-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-degrees for 1-2 h exhibited a better strength-ductility match.(c) 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).