Icosahedral and decagonal quasicrystals in the AlPdMg system

✍ Scribed by N. Koshikawa; K. Edagawa; S. Takeuchi

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 395 KB
• Volume: 181-182
• Category: Article
• ISSN: 0921-5093
• DOI: 10.1016/0921-5093(94)90745-5

✦ Synopsis

A Frank-Kasper (FK) type icosahedral phase, a Mackay icosahedron (MI) type icosahedral phase and a decagonal phase have been found to form in the A1-Pd-Mg system. This is the first example in which the three types of quasicrystalline phases are formed in the same alloy system. The formation ranges in the melt-quenched state are 5-20 at.% Pd and 20-45 at.% Mg, about 30 at.% Pd and 15-20 at.% Mg, and about 20 at.% Pd and 0-10 at.% Mg, for the FK-type icosahedral phase, MI-type icosahedral phase and decagonal phase, respectively. In particular, the FK-type icosahedral phase with the compositions around Al<~Pdt4Mg43 has been shown to be thermodynamically stable. Large grains of the order of 0.1 mm in size have been grown through slow solidification for the stable FK-type icosahedral phase. The stability of various FK-type icosahedral phases has been discussed in view of atomic packing efficiency and electron band structure energy.