Transmission-electron-microscopy studies of small dislocation loops in ${\mathrm{Al}}_{76}$${\mathrm{Si}}_4$${\mathrm{Mn}}_{20}$ icosahedral phase

Small dislocation loops with characteristic diffraction contrast of black-white lobes have been observed experimentally in annealed ${\mathrm{Al}}_{76}$ ${\mathrm{Si}}_4$ ${\mathrm{Mn}}_{20}$ quasicrystalline icosahedral phase by using transmission electron microscopy. The variation of the features of the diffraction-contrast images of the small dislocation loops with experimental conditions has been observed and computer simulated systematically. By taking the Burgers vector b and the normal n of the loops to be along the [100100] direction, i.e., parallel to one of the twofold symmetry axes, we have arrived at good agreement between the observed and computer-simulated features of the diffraction-contrast images.