Effect of rolling reduction on the deformation texture and anisotropy of transformation strain in Ti–50.2at.%Ni thin plates

Abstract

Abstract Ti–Ni shape memory thin plates with a thickness of ∼0.1 mm can be used for making two-dimensional shape actuators. Such thin plates were made by a rolling process, which will induce a specific texture in the plates. The texture causes an anisotropy of the transformation strain to appear. The purpose of the present study is to investigate the effect of a final cold-rolling reduction in the range of 0–70% on the texture and anisotropy of the transformation strain in Ti–50.2at.%Ni thin plates which were annealed at 673 K for 3.6 ks after the cold-rolling, the initial thickness being 0.2 mm. Transformation strains along various directions in the rolling plane were calculated by using a crystallite orientation distribution function (ODF) which was measured by an X-ray diffraction (XRD) method. The transformation strain in specimens prepared by intermediate cold-rolling reduction was almost constant along directions between 0 and 40° from the rolling direction, and it decreased with further increasing the angles until 90°. Specimens prepared by 0 and 70% cold-rolling reduction showed a maximum strain at an angle of 30°. Transformation strains were also measured by thermal cycle tests under various constant stresses. Both the calculated and experimentally obtained strains showed qualitatively a similar orientation dependence.