Stability, Chemical Composition, and Structural and Electronic Properties of the Intermetallic Compound τ4-(Al1-xSix)5Fe

Abstract

τ4-Al3Si2Fe particles form during casting of Al-based alloys. They have strong impacts on the solidification process and the mechanical performance of the products. Meanwhile, experiments revealed notable variations in lattice parameters and chemical compositions for the manufactured Al alloys, and knowledge about the intrinsic properties of the τ4-phase is still far from complete. We here investigate the crystal chemistry and electronic properties of the τ4-phase using a combination of ab initio modelling and thermodynamics analysis. The study justified the τ4-Al3Si2Fe superstructure at low temperature. There is a shallow potential valley in the formation energy vs Si content curve, corresponding to its compositional and structural flexibility. Thermodynamics analysis revealed kinetic effects on its chemical composition during casting. The obtained information helps understand the formation of and characterize the Fe-IMCs particles in Al alloys, and design novel Al alloys and manufacturing processes for recycling Al.