EDGE DISLOCATIONS IN ICOSAHEDRAL AL-PD-MN ALLOYS

Edge dislocations in the Al-Pd-Mn icosahedral phase have been first studied by electron diffraction contrast analysis and convergent-beam electron diffraction (CBED). Because of the severe residual contrast problem the direction of the Burgers vector in real space cannot be reliably determined by conventional electron diffraction contrast analysis. However, the defocus CBED technique has been successfully used to show that the Burgers vector can be uniquely characterized by six integers B = [01 - 110 - 1] in six-dimensional space. In real space the direction of the Burgers vector B(parallel-to) is parallel to a twofold axis and the size \B(parallel-to)\ is 0.291 nm. The dislocation possesses edge-type character in real space with the dislocation line parallel to another twofold axis.