Effect of interstitial carbon distribution and nickel substitution on the tetragonality of martensite: A first-principles study. (October 2017)

• Record Type: Journal Article
• Authors: Chentouf, S.; Cazottes, S.; Danoix, F.; Goune, M.; Zapolsky, H.; Maugis, P.
• Is Part Of: Intermetallics. Volume 89(2017)
• Page Start: 92
• Page End: 99
• Publication Date: 2017-10
• Subjects: Intermetallic compounds -- Metallography -- Periodicals; Metallic glasses -- Periodicals; Composés intermétalliques -- Métallographie -- Périodiques; 669.94
• DOI: 10.1016/j.intermet.2017.05.022
• Languages: English
• ISSNs: 0966-9795

Abstract

Abstract: By using first principles calculations, the effects of carbon distribution and of 25 at.% of nickel substitution on the tetragonality of ferrous martensite have been investigated. Different carbon concentrations have been considered (0≤xc ≤ 12.5 at.%). All calculations were based on the Projector Augmented Wave (PAW) method of the Density Functional Theory (DFT). The Special Quasirandom Structure (SQS) method has been used to model the disordered structures of the Fe16 C2X and (Fe, Ni)16 C2X systems. Our calculations demonstrate that the lattice parameters a and c vary linearly with carbon concentration, up to the high value of xc = 12.5 at.% (for X = 1). The nickel substitution enhances the expansion of parameter c of the Fe16 C2X system up to 37%. This trend is correlated with the shear moduli calculated for bcc-iron and the disordered Fe25 at.%Ni structure. The mixing energies of the Fe16 C2X and (Fe, Ni)16 C2X systems indicate that the unmixing of martensite by spinodal decomposition is favoured by the nickel substitution. It is shown that carbon-carbon interactions are mostly repulsive until the distance of two bcc-iron lattice parameters. Graphical abstract: Highlights: Lattice parameters of FeC martensite vary linearly with carbon concentration, upto the high value of Xc = 12.5 at.%. Nickel substitution enhances the expansion of c parameter of the FeC martensite by 37%. The unmixing of martensite by spinodal decomposition is favoured by the nickel substitution. Carbon-carbon interactions are mostly repulsive until the distance of two bcc-iron lattice parameters.