Deformation twinning in a face-centred icosabedral Al[sbnd]Cu[sbnd]Fe quasicrystal

We have determined the twinning mode in icosahedral Al65Cu23Fe12 deformed by high-temperature creep. The twinning elements K1; K2, η1, and η2 have been determined from electron diffraction experiments. Both of the invariant planes K1 and K2 were determined to be of the fivefold {1/00/1 0/0} type, and the two directions η1 and η2 were found to be midway between two twofold directions and of the 〈l/2 1/1 2/1〉or 〈1/10 1/3 0/1〉 types. Considering the large amount of shear strain accommodated by this twinning and the large number of possible twin planes, a substantial amount of plastic deformation can be accommodated by deformation twinning in these materials.