Structure and morphology of [icosahedral Al62Cu25.5Fe12.5]100−x[decagonal Al70Co15Ni15]x alloys, for (0∼3 and 5∼10)

Alloys made from mixtures of Al ₆₂Cu _25.5Fe _12.5 icosahedral quasicrystal (IQC) and Al ₇₀Co ₁₅Ni ₁₅ decagonal quasicrystal (DQC) were studied by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The transition from IQC to DQC was thus discussed by studying the evolution of their constituent phases in each alloy. Three approximant phases were found as common phases in most of the pseudo-binary alloys: λ-Al ₁₃Fe ₄, β-AlFe and τ3-Al ₃Ni ₂. It is found that, with the increment of the DQC content in the alloy, the λ phase changes from Al ₁₃Fe ₄ to Al ₁₃Co ₄ and the τ3 phase changes from Al ₃Cu ₂ to Al ₃Ni ₂. The formation of these phases were found also to follow the evolution of their corresponding e/ a -constant lines in the Al–(Cu,Ni)–(Fe,Co) pseudo-ternary phase diagram. Under this framework, the roles played by the related approximants in the transition process are briefly discussed.