Structural and thermal properties of Fe3Al, Fe3AlC and hypothetical Fe3AlX (X = H, B, N, O) compounds: Ab initio and quasi-harmonic Debye modelling

Atomistic modelling based on the Density Functional Theory (DFT) within the generalized-gradient approximation (GGA) and the quasi-harmonic Debye model were used to study the stability and thermal properties of Fe3Al, Fe3AlC and hypothetical Fe3AlX (X = H, B, N, O) compounds. The predicted values of cohesive energy indicate that the E21 Fe3AlC, Fe3AlB, Fe3AlN are stable compounds. The C addition has the highest effect in strengthening the cohesion of the Fe3Al base while, in contrast, H affects considerably its stability. The Fe3AlC (κ-carbide) phase has the highest bulk modulus and the evolution of its expansion coefficient with temperature is very close to that of Fe3Al. These features are important for possible applications of the Fe3AlC (κ -carbide) phase as strengthening precipitates in the Fe3Al system.