The phase transition between decagonal quasicrystal and (1/0, 2/1) approximant in Al20Si20Mn20Fe20Ga20 high entropy quasicrystal alloy

High-entropy quasicrystals contain both multiple principal alloying elements and complex crystal structures, in contrast to usual high-entropy alloys that have simple crystal structures; however, microstructures of high-entropy quasicrystal-related phases have seldom been revealed. In this paper, we report complex domains of approximants of high-entropy decagonal quasicrystal (HE-DQC) in Al20Si20Mn20Fe20Ga20 alloy, investigated by spherical aberration-corrected scanning transmission electron microscopy at atomic-level resolution. Importantly, a phase transition from HE-DQC to a (1/0, 2/1)–type orthorhombic approximant, with a = 0.73 nm, b = 1.23 nm, c = 2.24 nm, was revealed. We found that multi-point nucleations and growth of the oriented hexagonal structural blocks and phason flips of the basic structural blocks lead to this phase transition. This study benefits understanding of the formation of periodic structures in HE-DQC.