Texture development in near-α Ti friction stir welds

The microstructures and crystallographic textures produced during friction stir welding of the near-α Ti-5111 titanium alloy were characterized as a function of welding speed. The textures produced were compared with ideal hexagonal close packed (hcp) shear textures and with predicted textures of hcp Burgers variants of ideal body-centered cubic (bcc) shear textures, showing that the deposited welds are dominated by the hcp P1 and bcc D1 textures. The hcp P1 shear texture was dominant at slow weld speeds, while the bcc D1 shear texture was dominant at the fast weld speed. This variation appears to result from a poor transmission of the shear deformation from the rotating tool to the deposited weld that develops at faster welding speeds. These observations are compared to other studies of friction stir welds in hcp and bcc materials reported in the literature.