A combinatorial study on the influence of Cu addition, film thickness and heat treatment on phase composition, texture and mechanical properties of Ti–Ni shape memory alloy thin films

A series of amorphous Ti–Ni–Cu based thin films with compositional spread and different thicknesses was produced at room temperature using a magnetron sputtering device and crystallized by means of different heat treatments. Phase composition and crystallographic orientation of the films were characterized using a Multi-Axial X-ray Diffraction approach and their mechanical properties were assessed using nanoindentation. The results show that the addition of Cu and thermal treatments can be used to significantly alter the phase composition, the texture and the microstructure of the films. Film thickness plays an important role in determining of the amount of martensitic phase at room temperature as well as the amount of Ti-rich and Ni-rich phases. In particular a thickness threshold between 350 nm and 800 nm was shown to be critical for the triggering of the texture in the austenitic phase.