Structural Transition and Magnetic Property of Quasicrystalline Phases in Al–Cu–Fe–Cr Prepared by Mechanical Alloying and Heat Treatment

The present study investigated structural phase transitions in heat-treated mechanical alloyed Al₆₅Cu₂₀Fe_15−xCr_x (x = 2.5, 5, and 10). The Al, Cu, Fe, and Cr powder mixtures were mechanically alloyed by using a planetary ball mill for 30, 60, and 120 minutes. After 120 minutes of milling, Al₆₅Cu₂₀Fe_12.5Cr_2.5 and Al₆₅Cu₂₀Fe₅Cr₁₀ alloys showed β-AlFe(Cu) solid solution phase, and Al₆₅Cu₂₀Fe₁₀Cr₅ alloy showed τ-AlFe(CuCr) solid solution phase, but no quasicrystalline phase formed during the process. Elemental powders were milled for 30 minutes and heat-treated at 600 °C and 700 °C for 4 hours, resulting in solid-state reactions and forming ω, β, and i phases. Among these, the Al₆₅Cu₂₀Fe_12.5Cr_2.5 alloy powders had the highest i-phase content after annealing at 700 °C. SEM micrographs of samples annealed at 700 °C for 4 hours exhibited the formation of an icosahedron-shaped quasicrystalline phase with a particle size of about 1 to 2 μm. The powders showed soft ferromagnetic behavior at room temperature.