Microstructures and thermal stability of high-entropy decagonal quasicrystal approximant micropillars

Parallel micropillars of quasicrystal approximants are fabricated in Al₂₀Si₂₀Mn₂₀Fe₂₀Ga₂₀ high-entropy alloy via melt spinning, and their micromorphology is observed by scanning electron microscopy. Unlike the traditional quasicrystal system where the crystal structure of the decagonal prism is decagonal quasicrystal, the crystal structure of micropillars reported here is identified as the orthorhombic (1/0, 2/1) quasicrystal approximant (a = 0.73 nm, b = 1.23 nm, c = 2.24 nm) through transmission electron microscopy. The cross-section structure of the micropillars consists of multiple twinned (1/0, 2/1) approximant domains or alternating splicing of (1/0, 2/1) and defective (1/0, 2/1) quasicrystal approximants. The thermal stability and the microstructure evolutions of micropillars after being heat treated are also investigated. Meanwhile, the nanomechanical properties of micropillars are characterized.