Published online by Cambridge University Press: 21 February 2011
I review the current results of our group about high-resolution electron microscopy of the icosahedral quasicrystals, in particular, in rapidly solidified Al-Mn-Si and conventionally solidified Al-Fe-Cu alloys, by using 200 kV and 1 MV microscopes which have resolutions of .23 and .16 nm, respectively. High-resolution lattice images of Al-Mn-Si taken with the 200 kV microscope show characteristic features of a model of the three-dimensional Penrose tiling, and also show the existence of quenched phason strains and edge-type dislocations in the Al-Mn-Si and as-casted Al-Fe-Cu alloys. After annealing the stable Al-Fe-Cu icosahedral phase at 1118 K for 48 hr, quenched phason strains are almost relaxed and nearly perfect icosahedral symmetry is formed. A high-resolution structure image of Al-Mn-Si taken with the 1 MV microscope clearly shows an arrangement of the Mackay icosahedral atomic clusters.