Effect of Plastic Strain on Shape Memory Characteristics in Sputter-Deposited Ti-Ni Thin Films
Institute of Materials Science, University of Tsukuba, Tsukuba, Ibaraki 305, Japan
2 National Research Institute for Metals, 1-2-1 Sengen, Tsukuba, Ibaraki 305, Japan
The plastic strain which is introduced during cooling and heating under a constant stress has an influence upon the transformation and deformation characteristics of sputter-deposited Ti-Ni shape memory alloy thin films. With increasing the accumulated plastic strain, Ms rises and recovery strain increases. The changes in such characteristics are due to the internal stress field that is formed by plastic deformation. However, the change in Ms in Ti- 50.5at%Ni is larger than that in Ti-48.9at%Ni, although the plastic strain in the former is lower than that in the latter. In order to understand this point, the effective internal stresses were estimated in both alloys; the internal stress in the former is more effectively created by the introduction of plastic strain than in the latter.
© EDP Sciences