Effects of Deformation Twinning on the Deformation Behavior of Textured Titanium Sheets in Plane Strain Compressive Tests

Abstract

Plane strain compressive tests were carried out on five kinds of textured sheets of pure titanium. Some of the textures showed quite different pole figures while others, despite having similar pole figures, showed quite different relations of the orientations between neighboring grains. The deformation behavior of these sheets was studied in detail, with regard to the anisotropy, occurrence of deformation twinning, and twin systems.
Twin systems and the manner of the occurrence of the deformation twinning were classified according to the textures and the stress conditions. However, since the constraint to deformation is larger in the plane strain compressive tests than in uniaxial tension, there were differences from uniaxial tests both in the effects of orientation on the values of flow stress, and in the shearing directions of twins in test piece. Although grains whose ⟨0001⟩ orientation is nearly the sheet normal can be deformed easily by prismatic slip under uniaxial tension, in the plane strain compression grains with the same orientation showed much deformation twinning and flow stress was high. Therefore, even if the textures and the flow stress of the sheets were similar at early stages of deformation, the flow stress under plane strain compression was much greater than for uniaxial tension. In sheets with the conventional cold-rolled and recrystallization texture, the opposite anisotropy in plane was observed between the plane strain compressive and the uniaxial tensile tests.