Fabrication of Ti-Ni shape memory alloy films by unbalanced magnetron sputtering and their joule heat induced shape memory behavior

We have optimized the deposition conditions for fabricating Ti-Ni shape memory films by dc unbalanced magnetron sputtering using Taguchi method. The deposited films were annealed at 600C for 60 min for crystallization and memorization into a fiat shape after dissolving the Cu substrates. These films were subjected to DSC measurements and thermal cycling tests under a constant stress. The Joule heat induced shape memory behavior was also characterized by a specially designed tensile testing machine. The transformation temperature of Ni-rich films was found to be lower than RT. On the other hand, those of Ti-47-49.4 at%Ni films were higher than RT, which means they can be expected to show the shape memory effect at RT. The Ti-47-49.4 at%Ni films showed a perfect shape recovery under a constant stress by Joule heat of less than 0.1 J.