Enhanced mechanical property of Fe-Al alloy due to Mn insertion: ab initio study

We use ab initio density functional theory to examine the structural and mechanical properties of Fe-Al alloys at various Al concentrations with or without a small amount of Mn. For each disordered Fe-Al alloy, we consider sundry disordered configurations to determine the equilibrium structure. It is found that the disordered Fe-Al alloy with high Al content (∼25 at%) becomes less stable and more brittle than its ordered counterpart D03 second phase. To predict the ductility of Fe-Al alloys, we estimate Pugh's constant defined by the ratio between bulk and shear moduli and apply the Pugh's criterion. We find that an addition of a small amount of Mn may stabilize disordered solid solutions over the D03 second phase. Moreover, the Mn addition also improves its mechanical properties making the disordered Fe-Al alloy more ductile than D03.