Stability, electronic structures, and mechanical properties of Fe-Mn-Al system from first-principles calculations

The stability, electronic structures, and mechanical properties of the Fe-Mn-Al system were determined by first-principles calculations. The formation enthalpy and cohesive energy of these Fe-Mn-Al alloys are negative and show that the alloys are thermodynamically stable. Fe3Al, with the lowest formation enthalpy, is the most stable compound in the Fe-Mn-Al system. The partial density of states, total density of states, and electron density distribution maps of the Fe-Mn-Al alloys were analyzed. The bonding characteristics of these Fe-Mn-Al alloys are mainly combinations of covalent bonding and metallic bonds. The stress-strain method and Voigt-Reuss-Hill approximation were used to calculate the elastic constants and moduli, respectively. Fe2.5Mn0.5Al has the highest bulk modulus, 234.5 GPa. Fe1.5Mn1.5Al has the highest shear modulus and Young's modulus, with values of 98.8 GPa and 259.2 GPa, respectively. These Fe-Mn-Al alloys display disparate anisotropies due to the calculated different shape of the three-dimensional curved surface of the Young's modulus and anisotropic index. Moreover, the anisotropic sound velocities and Debye temperatures of these Fe-Mn-Al alloys were explored.