Transmission electron microscopy study of dislocation motion in icosahedral Al–Pd–Mn

Perfect and imperfect dislocations trailing phason faults in quasi-crystals are introduced using a simplified two-dimensional aperiodic structure. Then, on the basis of observations of deformed specimens as well as in situ experiments in a transmission electron microscope, the motion of dislocations in icosahedral Al–Pd–Mn is shown to take place exclusively by climb. Under such conditions, the very high brittleness of Al–Pd–Mn at low and medium temperatures is proposed to be a consequence of the difficulty of glide, which itself appears to be an intrinsic property of the quasi-crystalline structure.