Influence of thermal treatment on the subgrain parameters and microstructure of two-subgrain Al-Cu-Co single quasicrystals

The influence of low-temperature (100 degreesC) and high-temperature (900 degreesC) thermal treatment on the subgrain parameters i.e. misorientation angle, strain field, and microstructure of two-subgrain single quasicrystals of Al-Cu-Co alloy was studied. A banded microstructure was discovered in the single quasicrystals. The direction of the bands was found to be parallel to the tenfold symmetry axis. Low-temperature treatment induces a homogeneous strain field of macroscopic scale in the whole sample, causes fragmentation of the bands, and increases the boundaries' density. High-temperature thermal treatment at 900 degreesC carried out afterwards on the same samples causes some broadening of the bands which is connected with the partial disappearance of the boundaries. The treatment also causes disappearance of the homogeneous strain field and rotation of the subgrains in relation to one another about the tenfold symmetry axis. These observations are interpreted by describing the bands as anti-phase domains of the decagonal Al-Cu-Co alloy. (C) 2002 Elsevier Science B.V. All rights reserved.