ALCHEMI study of chemical order in Al-Cu-Co decagonal quasicrystals

Electron channelling patterns were obtained for two types of Al-Cu-Co decagonal quasicrystals prepared by the Bridgman and water-quenching methods. In both alloys, it was found that the three constituent elements, Al, Cu and Co, occupied specific sublattice sites that are different from each other, i.e. they are mutually ordered. As the melt-quenched sample even showed chemical order between Cu and Co, a strong correlation between Cu and Co is assumed to be maintained near to the melting temperature in Al-Cu-Co quasicrystals. The present results suggest a particular stabilization mechanism in the Al-Cu-Co quasicrystals, which differs from the Al-Ni-Co system where the two transition metals, Ni and Co, are mutually disordered.