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 (3d 5 4s 2 ) 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.

Mechanical Properties of Cementite

“…Table 7 59,86,91,[94][95][96][97][98] shows the nine independent C ij s values of cementite obtained by the first-principles calculations, their calculation methods, and the elastic constants of the polycrystalline cementite calculated from C ij s* 3 . The C ij s value of Reference 94) was larger than those in other studies because Reference 94) is in the NM state while the others are in the FM state.…”

“…The effect of the addition of alloying elements on the elastic constants of single-crystal cementite has been investigated using first-principles calculations. 59,97) Ghosh 59) calculated C ij s for Fe 2 CrC (4c sites in Fe 3 C are occupied by Cr), and Huang et al 97) calculated C ij s for Fe 2 MnC (8d sites in Fe 3 C are occupied by Mn). These C ij s and elastic constants are shown at the bottom of Table 7.…”

“…Compilation of elastic moduli (GPa) under zero pressure and at 0 K obtained from first-principles calculations by different authors in chronological order 59,86,91,[94][95][96][97][98]. …”