Density functional theory characterisation of cementite (Fe3C) with substitutional molybdenum (Mo) atoms

The presence of substitutional atoms, other than iron (Fe), in the cementite (Fe3C) phase in steels can have a beneficial influence on different mechanical and thermodynamic properties. For example, the addition of molybdenum (Mo), which tends to partition to cementite and stabilise it, can improve the hardness of the steel at higher temperatures. In order to better understand the effects of Mo as a substitutional element, an energetic, structural, electronic, and mechanical characterisation of cementite containing Mo atoms was performed. Formation enthalpies, densities of states, and the full stiffness tensors where calculated and analysed in terms of preferential occupation sites, stability, ductile/brittle behaviour, and isotropic and directional evolution of the elastic constants.