Anomalous structural evolution was induced in the equilibrium immiscible Co-Cu and Fe-Cu systems by 100 or 200 keV xenon ion irradiation at 77 K or room temperature. In the Co_(15)Cu_(85) and Fe_(70)Cu_(30) multilayered films, nanosized quasicrystals were formed in an amorphous matrix, through a two-step transition of crystal-to-amorphous-to-quasicrystal. The obtained quasicrystals are Co-Cu dodecagonal and Fe-Cu icosahedral phases with twelve-fold and five-fold rotational symmetries, respectively. The real compositions of the amorphous matrix were determined to be close to Co_(10)Cu_(90) and Fe_(70)Cu_(30), while those for quasicrystals are nearly Co_(20)Cu_(80) and Fe_(50)Cu_(50), respectively. Moreover, the same dodecagonal and icosahedral phases were also obtained in the specifically-designed Co_(50)Cu_(50) and Fe_(50)Cu_(50) multilayered samples upon thermal annealing at 500癈 and 850癈, respectively, confirming the existence of these new metastable states in the respective systems. Besides, our molecular dynamics study showed that either Co or Fe could be mixed with Cu at an atomic scale in forming some metastable alloy phases. The amorphous-to-quasicrystal transition was discussed in terms of the similarity in the atomic configuration between the quasicrystal and amorphous short-range orders.
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