Occurrence of faults/APBs in periodic to quasiperiodic transformations

The strip projection method has been used here to establish the structural relationships between various two dimensional quasiperiodic structures and certain well known periodic structures. These periodic structures, designated as unmodulated approximants, can transform into their quasiperiodic counterparts in a continuous fashion. The early stages of such transformations are characterized by the occurrence of faults or APBs. There is considerable high resolution electron microscopy (HREM) and electron diffraction evidence in favour of this in the case of the β-Mn to octagonal quasicrystal, the σ-phase to dodecagonal quasicrystal and the Al₅Ti₃ to quasiperiodic superlattice structure transformations.