Elastic constants and structural stability of non-stoichiometric epsilon ε-Fe2.4C carbide

While the elastic properties of cementite are known, there is no corresponding experimental or theoretical data available for the well-known hexagonal epsilon-Fe2.4C carbide. In this study we investigated the dynamical and mechanical stability of different configurational structures of the hexagonal epsilon-Fe2.4C carbide. A reliable structural model was established through the ground state energy and phonon calculations, and was used to calculate the elastic constants. The DOS calculations of that structure revealed a strong covalent bonding between Iron and C as shown by low occupation of states at the Fermi level. The calculated mechanical properties (i.e. Young's modulus Y and shear modultis G) of epsilon-Fe2.4C carbide surpass those of the ubiquitous theta-Fe3C cementite. The calculated elastic properties are predictions, which can be used as an input to establish reliable models for steel development.