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

Abstract

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.