Microcrystalline A1FeCu phase of pseudo icosahedral symmetry

It is at first recalled that a rhombohedral to icosahedral solid state transformation has been observed in an A1FeCu alloy. The cell parameters of the rhombohedral phase, defined in the trigonal system, are: a=32.08A and α=36 deg. C. This lattice can be, interestingly, defined by considering a larger rhombohedral unit cell with parameters, a=2τ3(4.45)A and α=63.43 deg. C, showing a direct relationship with the parameter of 4.45 τ3nA of the icosahedral state. In its microcrystalline state, the rhombohedral phase exhibit stellate configurations of twinned crystals, as identified by high resolution electron microscopy. These results, discussed with respect to previous works related to the atomic structure of quasicrystals, allow to confirm several propositions about icosahedral models constituted of icosahedral atomic clusters. (author). 21 refs, 10 figs