Development and characterization of shape memory Cu–Zn–Al thin films

Ternary Cu–Zn–Al alloys show good shape memory properties with narrow hysteresis and a wide range of martensitic transformation temperature (Ms), depending on the alloy composition. Thin films of Cu–Zn–Al with shape memory effect were grown for the first time using a new procedure. First Cu–Al thin films were obtained by DC sputtering on Si (1 0 0) substrates at room temperature, and second, the Cu–Al films were encapsulated and annealed in the presence of a Cu–Zn–Al bulk reference in order to fix a Zn vapour pressure. In this way a controlled amount of Zn is transported from the bulk reference into the film, in such a way that the Ms of the film becomes nearly the same as the bulk reference. The structures and microstructures of the as grown films were analysed by X-ray diffraction and transmission electron microscopy. The martensitic transformation temperature was determined by resistivity measurements.