Deformation mechanism of quasicrystals

Characteristics of the high-temperature compressive deformation behavior of icosahedral and decagonal quasicrystals are reviewed. In icosahedral quasicrystals, the true stress versus true strain relation shows a pronounced yield drop, followed by gradual softening towards a minimum at a large true strain of about 0.5 and then changes to hardening at higher strain; the yield and flow stresses are quite sensitive to temperature and strain rate. In decagonal quasicrystals, the yield stress depends weekly on orientation in spite of its anisotropic structure. In both types of quasicrystals, the yield stress is higher in higher quality samples. The deformation mechanism of the quasicrystals is discussed in terms of dislocations glide in the quasicrystalline lattice governed by the Peierls mechanism. The Peierls mechanism in quasicrystals differs from that in crystals in that the dislocation glide is accompanied by a phason atrain relaxation and the Peierls potential is not periodic but quasiperiodic.