By using the first-principles projector-augmented wave method, the phase stability together with the bulk modulus and magnetic moment were investigated in binary and ternary interstitial phases ε-Fe6Cx, ε-Fe6Ny and ε-Fe6CxNy (x,y = 0, 1, 2, 3 and x+y ≤ 3) with a hexagonal structure. The predicted bulk modulus and volume of the ε phases increase with increasing the interstitial content, while the calculated magnetic moment decreased. The present work indicated that the longer the distance between the interstitial atoms, the lower the energy of the ε phases, i.e. the interaction between the interstitial atoms was of repulsive nature. The presently predicted phase stability of the ε-Fe6CxNy phases provided helpful insights into understanding the processes occurring during carbonitriding in steel and the further development of magnetic (carbo)nitrides.

The Influence of Interstitial Distribution on Phase Stability and Properties of Hexagonal ε-Fe6Cx, ε-Fe6Ny and ε-Fe6CxNy Phases - a First-Principles Calculation. S.L.Shang, A.J.Böttger, Z.K.Liu: Acta Materialia, 2008, 56[4], 719-25