Dendrites of the icosahedral quasi-crystalline phase, in an Al matrix, were formed during the rapid solidification of Al90Mn5Fe5. Large numbers of these particles were found to be twinned, with one of the 5-fold symmetry axes being the twin axis, as established by means of tilting experiments in a transmission electron microscope. The twin relationship could be expressed in 60 different ways, by rotation about 7 different axes of the icosahedron and by using 12 different angles. In alloys with compositions of Al86Mn7Fe7 and Al80Mn10Fe10, icosahedral Al3Fe and -Al formed at wheel-surface velocities which were greater than 23.5m/s. The icosahedral phase in these alloys was not twinned. At a wheel velocity of 12m/s, only Al3Fe and -Al formed.

A.Singh, S.Ranganathan: Acta Metallurgica et Materialia, 1995, 43[9], 3539-51