Single quasicrystals of ${\mathrm{Al}}_{70}$${\mathrm{Pd}}_{21}$${\mathrm{Mn}}_9$ were plastically deformed by 25% under compression at 750 C. Both these samples as well as control samples of as-grown and heat-treated material were investigated by transmission electron microscopy. It was found that upon deformation the dislocation density increases by about 2 orders of magnitude. This provides the first direct evidence for quasicrystal deformation by a dislocation mechanism. The dislocations were found to have twofold and fivefold Burgers vector directions in physical space.

• Received 5 April 1993

DOI:https://doi.org/10.1103/PhysRevLett.71.549