Solidification of Al–Cu–Fe alloys forming icosahedral phase

The solidification of a series of Al–Cu–Fe alloys containing an icosahedral phase has been studied by scanning electron microscopy, energy-dispersive x-ray spectroscopy, powder x-ray diffraction, and differential thermal analysis. The constitution and morphology of alloys solidified at different rates are presented. The overall compositional range of the icosahedral phase was determined in as-cast, slowly solidified alloys and those annealed at 800 and 600 °C. The solidification of this phase follows closely the Al₃Fe–AlCu compositional direction. The first icosahedral phase solidified close to Al_65.5Cu_21.5Fe₁₃; its compositional region at 800 °C lies between about Al_64.5Cu₂₃Fe_12.5 and Al₆₂Cu_26.5Fe_11.5, while at 600 °C it lies between Al₆₂Cu_26.5Fe_11.5 and Al_60.5Cu_29.5Fe₁₀. The formation of the icosahedral and related structures observed in Al–Cu–Fe alloys is discussed.