Twinning of ordered icosahedral quasicrystals was studied by transmission electron microscopy of the melt-spun alloy. Some 10 dendrites of the icosahedral phase formed near to the wheel-side of the melt-spun ribbons. These twinned extensively, so that multiple twinning of the grains was observed. Regions which were about 1 in size were twin-related, through a common 5-fold axis, to several neighboring regions. The possible number of different twin orientations which could result from repeated twinning was infinite. Thus, the multiple twinning gave rise to a random symmetry of the entire grain. Depending upon the under-cooling which existed across the melt-spun ribbons, several related phases such as decagonal quasicrystals and crystalline monoclinic Al3Fe phases in a 10-fold multiply-twinned form were also observed.

A.Singh, S.Ranganathan: Acta Metallurgica et Materialia, 1995, 43[9], 3553-62