Nanoscale indentation behavior of pseudo-elastic Ti-Ni thin films

48.28 at.%Ti-51.72 at.%Ni thin films were prepared by magnetron sputtering and post-annealed at 450, 500, 550 and 600 deg. C, respectively. The evolution of structure, phase transformation and nanoscale indentation behavior of Ti-Ni thin film annealed at different temperature were investigated by X-ray diffractometer (XRD), differential scanning calorimetry (DSC) and nanoindention test, respectively. The results showed that the as-deposited Ti-Ni thin films were amorphous and crystallized after post-annealing. As the annealing temperature increased from 450 to 600 deg. C, both the content of parent phase (B2) and that of the precipitate phase (Ni4Ti3) increased. Both the phase transformation temperature and the micro-hardness of the annealed Ti-Ni thin films increased as well. Meanwhile, the pseudo-elasticity energy recovery ratio η first increased to the maximum value and then decreased with the increasing annealing temperature. It revealed that the annealed Ti-Ni thin film specimens exhibited the highest pseudo-elasticity degree with the largest η values under the load of 10 mN