Physical properties investigation of Fe1−xAlx (x ≤ 50%-at) alloys using DFT and Wagner-Schottky model

Abstract

Atomistic modeling based on the Density Functional Theory (DFT) is used to study the structural, magnetic, electronic and mechanical properties of Fe1−xAlx alloys (x ≤ 50%-at) with and without B, C and N additions over the selected range of Al atomic concentration. It is shown that a singularity around xAl ∼ 40%-at is observed for the lattice parameters while the magnetic moment decreases uniformly without unexpected trend. The enthalpies of formation indicate that the presence of B stabilizes the system for Al concentration in the range of 25%-at < xAl < 45%-at and the electronic properties are affected by B, C and N additions. The trends in Young modulus, bulk modulus, expected ductility (Pugh ratio) and Vickers hardness evolution are also estimated. N addition improves the Young modulus of alloy while C addition increases its ductility. By using the Wagner-Schottky model, temperature and composition dependences of thermal vacancies in B2-FeAl reveal that the double defect AlFe anti-sites and Fe vacancies are dominating in the Al-rich side at finite temperature. In addition, the diffusion phenomenon is observed for B, C and N atomic defects.