Simulation of kappa-Carbide Precipitation Kinetics in Aged Low-Density Fe-Mn-Al-C Steels and Its Effects on Strengthening

Fe-Al-Mn-C alloy systems are low-density austenite-based steels that show excellent mechanical properties. After aging such steels at adequate temperatures for adequate time, nano-scale precipitates such as kappa-carbide form, which have profound effects on the mechanical properties. Therefore, it is important to predict the amount and size of the generated kappa-carbide precipitates in order to control the mechanical properties of low-density steels. In this study, the microstructure and mechanical properties of aged low-density austenitic steel were characterized. Thermo-kinetic simulations of the aging process were used to predict the size and phase fraction of kappa-carbide after different aging periods, and these results were validated by comparison with experimental data derived from dark-field transmission electron microscopy images. Based on these results, models for precipitation strengthening based on different mechanisms were assessed. The measured increase in the strength of aged specimens was compared with that calculated from the models to determine the exact precipitation strengthening mechanism.