The Alloying Strategy to Tailor the Mechanical Properties of θ-Al13Fe4 Phase in Al-Mg-Fe Alloy by First-Principles Calculations

Abstract

As an important strengthening phase in Al-Mg-Fe alloy, the elastic and ductile–brittle characteristics of Al13Fe4 intermetallics hold prime significance in ascertaining the mechanical properties and potential application of Al-Mg-Fe alloys. In this study, multialloying of Co, Cu, Cr, Mn, and Ni has been adopted for tuning the mechanical characteristics of the Al13Fe4 phase; their effects on mechanical features and electronic structure of the Al13Fe4 phase have been scrutinized systematically by first-principles calculations employing the density functional theory. The replacement of Fe with M (M = Co, Cu, Cr, Mn, and Ni) is energetically advantageous at 0 K, as evidenced by the negative cohesive energy and mixing enthalpy of all Al13(Fe,M)4 phases. Cu and Ni, on the contrary, have a detrimental impact on Al13Fe4′s modulus and hardness due to the evolution of chemical bonding strength. Co, Cr, and Mn are thus, interesting candidate elements. In the light of B/G and Poisson’s ratio (σ) criteria, Al13Fe4, Al13(Fe,Cu)4, and Al13(Fe,Ni)4 have superior ductility; however, Al13(Fe,Co), Al13(Fe,Mn), and Al13(Fe,Cr)4 tend to be brittle materials. Calculation-based findings show that Co, Cr, and Mn are appropriate alloying elements for enhancing fracture toughness, whereas Mn reduces Al13Fe4′s elastic anisotropy. The electronic structure assessment found that the mechanical properties of the intermetallics are predominantly influenced by the Al-M bonds when the alloying element M replaced Fe.