Site preference of manganese in Mn-alloyed cementite

Abstract

The site preference of Mn in alloyed cementite is investigated by using X-ray diffraction (XRD) and first-principles calculations. First-principles calculations of the cohesive energies and formation energies of Mn-alloyed cementite indicate that Mn atoms prefer to substitute the 8d sites of cementite. The calculation results of density of states (DOS) and charge-density difference show that the more stable outermost electron orbital of Mn(3d54s2) may be the main reason for the site preference of Mn at 8d sites in Mn-alloyed cementite. In addition, the experimental XRD spectrum of 25 at.% Mn-alloyed cementite, which is prepared by using mechanical alloying combined with spark plasma sintering, highly coincides with the calculated XRD spectrum of Mn 8d-substituted cementite, verifying that Mn atoms prefer to substitute the 8d sites of alloyed cementite.