New type of decagonal quasicrystal with superlattice order in Al–Ni–Co alloy

A new type of decagonal phase having superlattice order has been found in an AI70Ni15Co15 alloy by means of the electron diffraction technique. Most of the grains in the Al70Ni15Co15 sample heat treated at 600°C for 216h exhibit superlattice order. In contrast, superlattice order has not been seen for the Al65Cu20Co15 decagonal phase. The relation between the structures with and without superlattice order is discussed using a four-dimensional description of the decagonal quasicrystalline structure.