Five-fold symmetry structure inhibiting the growth of an otherwise perfect η2 phase in Al-Zn-Mg-Cu alloys

Abstract

Using high angle annular dark-field scanning transmission electron microscopy, we report the formation of a five-fold symmetry structure at the (1¯100)η//(110)Al edge interface of otherwise defect-free η2 precipitates in Al-Zn-Mg-Cu alloys. This quasicrystal entity has a demonstrated ability to hinder growth at the interface where it resides. Assisted by calculations based on density functional theory, the five-fold symmetry structure is shown to form easily at Zn-rich conditions due to favorable interfacial energies at all stages of evolution. These findings offer an enhanced perspective of precipitate stabilization in an alloy of widespread industrial interest, presenting a potential alternative path to alloy design.