Fabrication of Al–Cu–Fe particles containing quasicrystalline i-phase by oxidation of ω-phase in air

Alumina-layer-coated spherical particles composed of ω-phase (Al₇₀Cu₂₀Fe₁₀) and icosahedral quasicrystal phase (i-phase, Al₆₄Cu₂₄Fe₁₂) in the Al–Cu–Fe system were fabricated by heating spherical particles of the ω-phase at 700 °C for 200–400 h in air. Differential thermal analysis and transmission electron microscopy observations suggested that formation of a liquid phase with a composition close to θ-phase (Al₂Cu) was formed near the surface of the particles, and an i-phase domain grew in the interior of the particles through the liquid. When the ω-phase particles were heated at 730 °C, which was above the melting point of the ω-phase, for 96–400 h in air, oxide-layer-coated granular particles containing the i-phase as the main phase and λ-phase (Al₁₃Fe₄) and θ-phase as minor phases were obtained. The surface oxide layer acted as a micro-crucible that could hold liquid and prevent cohesion to other particles.