FIVEFOLD AND THREEFOLD-TYPE DISLOCATIONS IN AN AL-CU-FE ICOSAHEDRAL QUASI-CRYSTAL IDENTIFIED BY DEFOCUS CONVERGENT-BEAM ELECTRON-DIFFRACTION

Dislocations with Burgers vectors b5 = [-211111] and b3 = [10-10-10] i n an Al-Cu-Fe icosahedral quasicrystal (IQC) have been identified for the first time by the defocus convergent-beam electron diffraction met hod. Unlike the dislocations already found in IQCs, the Burgers vector components of these two types of dislocation in physical space are pa rallel to the fivefold and threefold axes respectively of the IQC. In addition, the magnitudes of the Burgers vector components in physical space are about 0.2 and 0.5 nm respectively, which are only about one eighteenth and one quarter of those in the complementary space.