Annealing-induced icosahedral glass phase in melt-spun Al-Cu-V and Al-Si-Mn alloys

Structures of amorphous and icosahedral phases in Al75Cu15V10 and Al53Si27Mn20 alloys have been studied by x-ray and electron diffraction, and high-resolution electron microscopy. X-ray peak widths of the icosahedral phase in both alloys show a linear dependence on phason momentum. The high-resolution image of the icosahedral phase of Al75Cu15V10 shows an atomic arrangement similar to that described by the icosahedral-glass (IG) model. The lattice image shows a two-dimensional tiling pattern comprised mainly of pentagons joined together side by side randomly and filled with unique tearlike and cracklike defects exhibited in the IG model. Despite the high degree of structural defects of the IG phase, the characteristic physical properties of quasiperiodic lattices such as high electrical resistivity, high hardness, and large elastic modulus strongly persist in the IG phase.