In-Situ HREM Observation of the Structural Change from a Fundamental-Lattice Decagonal Quasicrystal of Al72Ni20Co8 to the S1 Type Superlattice Phase.

A structural change of an Al72Ni20Co8decagonal quasicrystal into the S1-type superlattice ordered phase has been observed at about 400°C by in-situ high-resolution electron microscopy. It is considered that the formation of the S1-type superlattice order is attributed to the structural change of the atom cluster with 2 nm diameter from mirror symmetric one to fivefold symmetric one and the disappearance of 1.2-nm intercluster bonds. [ABSTRACT FROM AUTHOR]