Gold with a martensitic transformation: Which opportunities?

In this paper we will consider an overview of the precious alloys that could be of interest due to the inherent properties of the thermoelastic martensitic transformation that they exhibit. For sure one of the main representatives of these materials can be considered the AuAlCu system (and the related well known Spangold TM ). Actually in the literature, since the late '70s, other systems have been indicated of interest but they knew a very limited success. We refer here to some pioneering work from G.B. Brook In more recent time the increasing experience in the science and technology of conventional shape memory alloys like NiTi (which in the meantime successfully reached the application field) brought a new interest for a clear understanding of the potential of these gold alloys. Here we report on results obtained in the three areas: spangold-like alloys, AuCuZn alloys, and a ternary modification of NiTi, i.e. NiTiAu. The samples used for the investigation have been prepared starting from pure metals and thoroughly investigated by means on differential scanning calorimetry, X-ray diffraction at different temperatures and optical microscopy. When possible the samples were submitted to simple recovery test to verify the amount of shape memory and/or pseudoelastic properties.