AuCuAl shape memory alloys for use in nano-actuators

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Australian Institute of Physics
Although Al, Au and Cu each has the face centered cubic structure in elemental solid form, they do not readily alloy with one another, and instead form a series of binary and ternary intermetallic compounds. The ternary system is very interesting and contains, amongst other features, an 18-carat shape memory electron compound sometimes called ‘Spangold’ [1] ( Figure 1). Shape memory alloys are remarkable in that they have the ability to return to their initial state and shape after being deformed. This ability arises from a martensitic (displacive) phase transformation (see Figure 2), which is strongly influenced by temperature, crystal structure and degree of ordering. It is already known that the parent phase of ‘Spangold’ must contain at least a minimum degree of ternary ordering before the reversible displacive transformation needed for the shape memory effect can take place [3]. Furthermore, the parent phase has been found to have the L21 ordered body-centered cubic packing arrangement [4], while it has been reported that the martensite can be described using a monoclinic unit cell [5]. Here we examine the possibility of using this compound as a nano-actuator. Magnetron sputtering was used to deposit the Au, Cu and Al. The films were then characterized using x-ray reflectometry (see figure 3), grazing incidence X-ray diffraction, scanning electron microscopy and atomic force microscopy. The properties of these films are compared with that of bulk samples.
Shape memory effect, Alloys, Actuators, Intermetallic compounds, Phase transformations, Crystal structure, Electron microscopy, X-ray diffraction
Bhatia, V. K., Kealley, C. S., Thorogood, G. J., Dowd, A., & Cortie, M. B. (2010). AuCuAl shape memory alloys for use in nano-actuators. Poster presented to the 34th Annual Condensed Matter and Materials Meeting 2010, Waiheke Island Resort, Waiheke, Auckland, New Zealand 2 - 5 February 2010. Retrieved from: