<i>Ab initio</i> modelling of the interface energy α-Fe/Fe₃c with the Bagaryatskii type orientation

Abstract

Perlite is one of the main structural constituents of carbon and low-alloy steels. In it, between the bcc ferritic and orthoboric cementite phases of Fe3C, the orientational relation (OR) of Bagaryatskii, Isaichev, and Pitch can be observed. The first two, which are close to each other and are not always, repeated in the experiment, predominate in low-temperature pearlite, which has the highest strength. In this study, the simulation "from first principles" by the DFT method in the WIEN2k software package of the structure and energy of coherent α-Fe/Fe3C interfaces was carried out. The supercells were subjected to structural and volume optimization. Calculations of the surface energy of the interphase boundaries gave the values of 0.383 J/m2 for the Bagaryatskii OR and 0.594 J/m2 for the Isaichev OR. This agrees well with the existing experimental values and the results of other molecular dynamics and first-principles calculations. The difference in surface energy can play a significant role for low-temperature pearlite with a small thickness of ferrite and cementite plates and a large area of interfacial boundaries per unit volume.