TEXTURE AND MECHANICAL ANISOTROPY IN COLD-ROLLED AND ANNEALED PURE TI SHEETS

Hot rolled bands of pure Ti obtained by thermomechanical treatments were cold rolled by varying rolling reductions between 50 and 90 %. By annealing these specimens at 750-degrees-C for 1h, the effect of cold rolling reductions on the development of the annealing texture was systematically investigated with the crystallite orientation distribution function analysis. Also yield stresses and r values of these specimens were determined and their anisotropics were correlated with their textures. It was found that the main orientation of the annealing texture was always (T013) [1210). It increased significantly with increasing rolling reduction up to 80 %. At higher rolling reductions, it decreased remarkably. Both yield stresses and r values of these specimens showed pronounced anisotropics, giving minimum values at the rolling direction, and increasing linearly with increasing angle to the rolling direction. By using Sachs' model of polycrystal deformation and by assuming only prismatic slip as the deformation mode, these anisotropies were predicted from the orientation distribution functions of these specimens. Anisotropies of the yield stress calculated with this method agree qualitatively well with those observed experimentally. However, disagreements between calculated and observed anisotropies of r values were considerably large. It was concluded that, since r values were measured after tensile straining of about 10 %, contributions of twinning cannot be neglected in the calculation.