DISLOCATIONS AND PLASTICITY OF QUASI-CRYSTALS

The experimental observations on dislocations in quasicrystals are rev iewed with particular emphasis on contrast behaviour in transmission e lectron microscopy. Quantitative contrast experiments indicate that th e phason-strain held of dislocations in icosahedral Al-Cu-Fe is by abo ut an order of magnitude stronger than the phonon-strain field. The da ta on room-temperature plastic deformation of quasi-crystals are revie wed. Depending on the ahoy, Vickers hardness values range from about 4 00 to 1000. Microcracks are observed under the Vickers indentations. T he hardness decreases steeply with increasing temperature. Controlled single-quasicrystal experiments indicated that high-temperature deform ation is carried by a dislocation mechanism.