Icosahedral quasicrystalline and hexagonal approximant phases in the Al-Mn-Be alloy system

Kim, SH and Song, GS and Fleury, E and Chattopadhyay, K and Kim, WT and Kim, DH (2002) Icosahedral quasicrystalline and hexagonal approximant phases in the Al-Mn-Be alloy system. In: Philosophical Magazine A & B, 82 (8). pp. 1495-1508.

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Abstract

We report the formation of a primitive icosahedral quasicrystal with increased stability in Al Mn-Be alloys close to the compound Al15Mn13Be2, by melt spinning and injection casting. The crystal structure of this compound was unknown. We show that in as-cast as well as heat treated condition the intermetallic phase H1 has a hexagonal structure with lattice parameters a = 1.2295 run and c = 2.4634 nm. The space group is P6(3)/mmc In the injection-cast samples, the quasicrystal coexists with another closely related hexagonal phase H2 with a = 1.2295 nm and c = 1.2317 nm with a possible space group of P6/mmm. This phase exhibits specific orientation relationships with the icosahedral quasicrystal given by [0001](hex)//2f(QC) and [01 (1) over bar0](hex)//5f(QC) where 2f(QC) and 5f(QC) represent twofold and fivefold axes respectively. Electron diffraction patterns from both phases exhibit a close resemblance to the quasicrystalline phase. It is shown that the H1 phase is closely related to mu-Al4Mn with the same e parameter while the a parameter is reduced by tau. Following Kreiner and Franzen, it is postulated that both structures (H1 and H2) can be understood by a simple hexagonal packing of I13 clusters.

Item Type:	Journal Article
Publication:	Philosophical Magazine A & B
Publisher:	Taylor and Francis Group
Additional Information:	Copyright of this article belongs to Taylor and Francis Group.
Department/Centre:	Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited:	19 Jul 2011 05:51
Last Modified:	19 Jul 2011 05:51
URI:	http://eprints.iisc.ac.in/id/eprint/39237

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