{alpha}-AlMnSi phase to a bcc structure by Xe{sup +} ion-beam irradiation

Conference · Tue Dec 31 04:00:00 EST 1996

OSTI ID:468918

Guo, Y X; Wang, L M; Ewing, R C ^[1]

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1. Univ. of New Mexico, Albuquerque, NM (United States)

AlMnSi alloy system has attracted great attentions since the first report on the icosahedral quasicrystal materials in 1984. The rapidly quenched AlMnSi alloy around the stoichiometry of the {alpha}-AlMnSi phase ({alpha}-phase below) may form icosahedral quasicrystals. And the structure unit of the {alpha}-phase is of near icosahedral symmetry. The {alpha}-phase has a cubic structure with space group Pm3 (a=1.268 nm). In each unit cell there are 138 atoms. The most important structure unit in this phase is the so-called MacKay icosahedron. In such a structure unit, 12 Al atoms are decorating the vertices of an icosahedron. Surrounding this icosahedron is another same oriented icosahedron of 12 Mn atoms, which is about twice the diameter of the former. Furthermore, 30 Al atoms define a shell outside the two inner icosahedra with each atom sitting distorted and are connected along those of their three fold axes that coincide with the <111> direction of the cubic lattice. The two triangular faces of the Mn icosahedron make up an Mn octahedron. Hence, two MacKay icosahedra define two basic positions as if in a bcc cell with a total of 108 atoms. The rest 30 atoms of light elements (Al or Si) in the structure serve as glue atoms that fill up gaps among the slightly distorted icosahedra. Electron diffraction pattern of this primitive cubic phase is shown in figure 1a, which is in [001] zone axis.

• DOE Contract Number: FG03-93ER45498
• OSTI ID: 468918
• Report Number(s): CONF-960877--
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM SILICIDES
IRRADIATION
MANGANESE SILICIDES
PHASE TRANSFORMATIONS
PHYSICAL RADIATION EFFECTS
XENON IONS