| The solidification sequence and the formation of the stable quasicrystalline icosahedral phase were investigated in a conventionally cast Al_(65)Cu_(20)Fe_(15) ingot by the combined analysis of SEM-EDX, TEM, XRD, and DTA. An Al_(65)Cu_(20)Fe_(15) alloy was melted in an inductively heated crucible, and then cast into a liquid nitrogencooled wedge-type steel mold under a dynamic argon atmosphere. Rapidly solidified ribbons were also prepared by single roller melt spinning. The microstructural evolution and the formation of icosahedral phase were examined as a function of heat treatment at the solid-liquid mixed region. Icosahedral phase was observed to form at the boundary of λ-Al_(13)Fe₄ phase via a peritectic reaction, and τ-AlCu(Fe) phase was formed in the remaining liquid. The composition corresponding to ω-Al_7Cu₂Fe was also detected in the area of icosahedral phase. It is suggested that the detailed solidification sequence and the resultant morphology of an Al-Cu-Fe alloy are subject to change as a function of cooling rate during solidification and heat treatment condition. |
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