Determination of martensite structures of the Au<inf>7</inf>Cu <inf>5</inf>Al<inf>4</inf> and Au<inf>7</inf>Cu<inf>5.7</inf>Al<inf>3.3</inf> shape-memory alloys

Publication Type:
Journal Article
Citation:
Acta Materialia, 2014, 79 pp. 234 - 240
Issue Date:
2014-08-19
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The β-phase of Au 7 Cu 5 Al 4 undergoes a reversible shape-memory phase transformation for which several conflicting martensite phases have been reported. Here we show the significance of the cooling temperature used to obtain the martensite. If Au 7 Cu 5 Al 4 is cooled from the parent phase condition to cryogenic temperatures, e.g. below 200 K, the martensitic phase is orthorhombic (space group Pcmn, a = 4.4841 Å, b = 5.8996 Å, c = 17.8130 Å); however, when this composition is cooled to only ∼260 K it will in general consist of a mixture of orthorhombic and monoclinic phase (the latter has space group P2 1 /m, a = 4.4742 Å, b = 5.9265 Å, c = 13.3370 Å, β = 91.425°). In contrast, a sample with decreased Al content (Au 7 Cu 5.7 Al 3.3 ) transforms fully to monoclinic phase if cooled to ∼260 K. © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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