The Role of Temperature and Magnetic Effects on the Stacking-fault Energy in Austenitic Iron

We have investigated the role of temperature and magnetic effects on the stacking-fault energy (SFE) in pure austenitic iron based on Density Functional Theory (DFT) calculations. Using the axial next-nearest-neighbor Ising (ANNNI) model, the SFE is expanded in terms of the free energiesof bulk with face-centered cubic (fcc), hexagonal close-packed (hcp), and double-hcp (dhcp) structures. The free-energy calculations require the lattice constant and the local magnetic moments at various temperatures. The earlier is obtained from the available experimental data, while the later is calculated by accounting for the thermal magnetic excitations using the Monte-Carlo tech- niques. Our results demonstrate a strong dependence of the SFE on the magnetic effects in pure iron. Moreover, we found that the SFE increases with temperature.