Preparation And Property Of Ti-Ni-Cu Shape Memory Alloy Thin Films

Deposition of Ti-Ni-Cu thin film was performed using a DC magnetron sputtering technique. The Ti49.83Ni40.37Cu9.8 thin films were prepared the echnique and annealed at 500, 600 and 700℃ for 1min, 0.5h, 1h and 2h. Effect of annealing the temperature and annealing time on Martensitic transformation behavior, phase composition and mechanical properties of Ti49.83Ni40.37Cu9.8 thin film was investigated by using tensile tests, XRD, SEM, TEM and DSC measurement.First, by the investigate of preparation method, it is found that by using single target DC magnetron sputtering technique a highly repeatable Ti Ni Cu thin film was preparated. Compared with Si slide, Si O2 slide and piezoid, using glass slide as substrate, the film was easy to separate from substrate, and had a good mechanical property. The Ar pressure affect the quality of Ti Ni Cu thin film obviously, when using the same sputtering power, a Ar pressure of 0.12 Pa makes the thin film have the best mechanical behavior. Also the sputtering power affect the composition of Ti Ni Cu thin film, with the increase of sputtering power, the content of Ni increases, while the content of Ti and Cu decreases. In the end, we choose 220 W, glass substrate, Ar pressure 0.12 Pa as the process of plating.By analyzing the phase composition of Ti Ni Cu thin film, we know that,at room temperature, Ti49.83Ni40.37Cu9.8 thin film annealed at 500℃, 600℃ and 700℃ is mostly made of B19’ Martensitic phase, but in the film annealed at 700℃ for 2h, the major phase becomes B2. As the annealing time and the annealing temperature increasing, the Ti(Ni,Cu)2 precipitates content increases. By analyzing the phase transformation temperature of different annealing method annealed Ti49.83Ni40.37Cu9.8 thin film, we know that, the film annealed for only 1 min has a high transformation temperature. For the film annealed in traditional method, the transformation temperature increases with the increasing annealing time. But in the film annealed for 2h, the transformation temperature decreases obviously.At last, by the investigation of the mechanical properties, we know that annealing method highly affects the mechanical properties of Ti49.83Ni40.37Cu9.8 thin film. As the annealing time εf increases, the film annealed at 500℃ for 1h has the best mechanical properties, the εf tested at room temperature is as high as 32%, which is the best in this experiment. By the stress and strain curve tested at different temperature, it is found that during 60~85℃ Ti49.83Ni40.37Cu9.8 thin film annealed at 500℃ for 1h has a good superelasticity. The film tested at 70~80℃ also show a two step phase transformation, which shows as the two yield point elongation in the stress strain curve. When tested at 60℃ the completely recoverable strain is as high as more than 12%, whih a good repeatability.