Crystal structure, thermodynamics, magnetics and disorder properties of Be-Fe-Al intermetallics

TL;DR

This study uses density functional theory to explore the structural, thermodynamic, magnetic, and disorder properties of Be-Fe-Al intermetallics, revealing new stable phases and temperature-dependent behaviors relevant to Be alloys.

Contribution

It identifies a novel structure for the Be-Fe binary { extepsilon} phase and predicts how Al additions influence phase stability and order/disorder transformations.

Findings

FeBe_5 forms above ~1250 K without Al.

{ extepsilon} phase stable below ~1650 K.

Al stabilizes FeBe_5 over FeBe_2 and { extepsilon}."],"paper_type":"empirical"}}# Answer: {

Abstract

The elastic and magnetic properties, thermodynamical stability, deviation from stoichiometry and order/disorder transformations of phases that are relevant to Be alloys were investigated using density functional theory simulations coupled with phonon density of states calculations to capture temperature effects. A novel structure and composition were identified for the Be-Fe binary {\epsilon} phase. In absence of Al, FeBe_5 is predicted to form at equilibrium above ~ 1250 K, while the {\epsilon} phase is stable only below ~ 1650 K, and FeBe_2 is stable at all temperatures below melting. Small additions of Al are found to stabilise FeBe_5 over FeBe_2 and {\epsilon}, while at high Al content, AlFeBe_4 is predicted to form. Deviations from stoichiometric compositions are also considered and found to be important in the case of FeBe_5 and {\epsilon}. The propensity for disordered vs ordered structures is also important for AlFeBe_4 (which exhibits complete Al-Fe disordered at all temperatures) and FeBe_5 (which exhibits an order-disorder transition at ~ 950 K).