1. Determination of martensite structures of the Au7Cu5Al4 and Au7Cu5.7Al3.3 shape-memory alloys.
- Author
-
Elcombe, Margaret M., Kealley, Catherine S., Bhatia, Vijay K., Thorogood, Gordon J., Carter, Damien J., Avdeev, Maxim, and Cortie, Michael B.
- Subjects
- *
GOLD compounds , *MARTENSITIC structure , *SHAPE memory alloys , *TEMPERATURE effect , *SPACE groups , *PHASE transitions , *CRYOGENICS - Abstract
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 P 2 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. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF