Cr-Fe

Abstract: A new potential for the iron–chromium (Fe–Cr) alloy system was optimized for the embedded-atom method (EAM) within the two-band model (TBM) extension. In contrast to previous works, free model parameters are predominantly adapted to available experimental high-temperature data of the mixing enthalpy. As a major improvement, the metastable α/α' miscibility gap is accurately described in agreement with experimental data and a recent CALPHAD parametrization. The potential was also fitted to obtain an enriched solubility for chromium atoms in an iron matrix at 0 K, as it is predicted by several ab initio calculations. Furthermore, it was benchmarked against phonon excess entropies at 300 K and 1600 K demonstrating good agreement with respective results of inelastic neutron scattering.

Abstract: We present an Fe–Cr interatomic potential to model high-Cr ferritic alloys. The potential is fitted to thermodynamic and point-defect properties obtained from density functional theory (DFT) calculations and experiments. The developed potential is also benchmarked against other potentials available in literature. It shows particularly good agreement with the DFT obtained mixing enthalpy of the random alloy, the formation energy of intermetallics and experimental excess vibrational entropy and phase diagram. In addition, DFT calculated point-defect properties, both interstitial and substitutional, are well reproduced, as is the screw dislocation core structure. As a first validation of the potential, we study the precipitation hardening of Fe–Cr alloys via static simulations of the interaction between Cr precipitates and screw dislocations. It is concluded that the description of the dislocation core modification near a precipitate might have a significant influence on the interaction mechanisms observed in dynamic simulations.

Abstract: The concentration-dependent embedded atom method (CD-EAM) is a powerful model for atomistic simulation of concentrated alloys with arbitrarily complex mixing enthalpy curves. In this paper, we show that in spite of explicit three-body forces, this model can be implemented quite simply with a computational efficiency comparable to the standard EAM for molecular-dynamics (MD) simulations. Ready-to-use subroutines for the parallel MD code LAMMPS can be provided by the authors upon request. We further propose an improved version of this potential that allows for very efficient calculations of single-particle displacement/transmutation energies, while retaining the complexity implicit in the three-body interactions. This enables large-scale Monte-Carlo simulations of alloys with the interatomic interactions described by the CD-EAM model.

Abstract: We have developed a two-band model of Fe-Cr, fitted to properties of the ferromagnetic alloy. Fitting many-body functionals to the calculated mixing enthalpy of the alloy and the mixed interstitial binding energy in iron, our potential reproduces changes in sign of the formation energy as a function of Cr concentration. When applied in kinetic Monte Carlo simulations, the potential correctly predicts decomposition of initially random Fe-Cr alloys into the α-prime phase as function of Cr concentration.

Abstract: By fitting a potential of modified Finnis–Sinclair type to the thermal expansion of ferromagnetic Fe and paramagnetic Cr, stability of the <110> self-interstitial atom is obtained. The resulting potentials are relatively hard, yielding high SIA formation energies. Less hard potentials give lower interstitial formation energy, but predict too small thermal expansion. We also show that the formation energy of the <111> SIA depends on distances in-between the 2nd and 3rd neighbour. By raising the value of the pair potential in this region, the energy difference with respect to the <110> configuration calculated with VASP in the PAW approximation can be reproduced.

Abstract: A semi-empirical atomic potential, the second nearest-neighbor MEAM, has been applied to obtain an atomic potential for the Fe-Cr system, based on the previously developed potentials for pure Fe and Cr. The procedure for the determination of potential parameter values and the performance of the assessed alloy potential were also presented. It was shown that the potential describes the basic thermodynamic property and alloy behavior in the bcc solid solution successfully, as well as many physical properties of pure Fe and Cr. The limit in the applicability of the present potential is also discussed.