Production and characterization of Cu-Al-Ni shape memory thin films

Abstract
The shape memory effect (SME) occurs in many alloy systems, the best known of which are NiTi, CuZnAl and CuAINi. These alloys are used to an inereasing degree for industrial applications (medical technology, fixing solutions). At the same time the efforts head for a miniaturisation of the components with regard to applications as integrated parts of so called intelligent structures. For this reason attempts were made to produce thin films by PVD coating with an alloy Cu-25.8AI-3.6 Ni at%, which shows the characteristic properties of a shape memory material. First of all attention was paid to the substrate material, on which the CuAlNi thin film was sputtered. On the other hand the sputter parameters (Ar-gas working pressure, electrical power, substrate temperature and time) were tested out in order to produce an easily removable, good quality thin film. After sputtering the thin film was removed from the substrate and heat treated to get a shape memory effect. DSC, TEM, SEM and XRD investigations were made to characterise the film morphology and to prove the shape memory effect. It was observed that a variation of the sputter parameters, mainly Ar-gas working pressure and power, leads to changes in the microstructure of the thin film, which furthermore influence the shape memory properties.