Effects of alloying elements on the stability and mechanical properties of Fe3Al from first-principles calculations

Abstract

The effects of 3d transition-metal alloying elements (V, Cr, Mn, Co, Ni, and Cu) on the structural stability, mechanical properties, and electronic structure of Fe3Al alloys have been investigated using first-principles calculations. The site preference of the alloying elements was clearly observed from the formation enthalpy calculations of the Fe3Al-X alloys. With regards to their mechanical properties, it was found that the alloying elements V, Cr, and Ni improve the ductility of the alloys by increasing Pugh's ratio, whereas Mn, Co, and Cu cause the materials to be more brittle. Among the tested alloying elements, V leads to the largest increase of Pugh's ratio as well as significant reduction in the alloy's elastic anisotropy, which implies that Fe3Al-V should have an enhanced ductility. An electronic structure analysis showed that the alloying elements altered the density of states of the alloys. From the projected density of states and from a crystal orbit Hamiltonian population analysis, it could clearly be seen that V leads to the stabilization of Fe3Al-V by reducing the magnetic moment and by relaxing the spin asymmetry of the Fe atoms. This result is in good agreement with that of a previous experiment, which reported that the alloy Fe3Al-V has an enhanced strength. However, Ni has antibonding states at the Fermi level that are substantially filled, which was found to be detrimental to the structural stability of the Ni alloy. (C) 2018 Elsevier B.V. All rights reserved.