Structural changes of Ni-rich Al–Co–Ni decagonal quasicrystals

The phase relationship among three Al-Co-Ni decagonal quasicrystals in a Ni-rich decagonal phase, and their phase changes, have been studied by electron diffraction and high-resolution transmission electron microscopy, as well as thermal analysis. At 1173 K, the so-called Ni-rich basic decagonal quasicrystal exists in a Ni-rich region from Al 72 Co 8 Ni 20 to Al 70 Co 10 Ni 20 , and transforms into the Sl-type ordered decagonal quasicrystal in Al 71 Co 10 Ni 19 . The Ni-rich basic decagonal quasicrystal at 1173 K in Al 72 Co 8 Ni 20 transforms into the Sl-type decagonal quasicrystal by annealing at 923 K, whereas the S1-type quasicrystal at 1173 K in Al 71 Co 10 Ni 19 alloy transforms into the type-I ordered decagonal quasicrystal by annealing at 923 K.