X-RAY MICROBEAM CHARACTERIZATION OF THE NEAR SURFACE NANOSTRUCTURED LAYER IN Ti AFTER FRICTION STIR PROCESSING

Plastic deformation and structural changes of a Ti surface after Friction Stir Processing (FSP) were analyzed by means of SEM, EBSD and advanced 3D polychromatic X-ray micro dif- fraction at the APS synchrotron. Spatially resolved 3D Laue diffraction allowed observing the changes in dislocation arrangement with depth in different regions of the FSP Ti. Formation of two specific zones was established: friction stir zone (FSZ), with an average thickness of 300 µm, and thermomechanicaly affected zone (TMAZ) with a thickness of 800 µm. It was shown that FSP generates a large number of dislocations. Maximal dislocation density is located within the TMAZ. Dislocation density gradually decreases and reaches the value typical for base metal. Within the TMAZ dislocations are distributed inhomogeneously. Inhomogeneity of plastic deformation and dislocations arrangement is found in 3D both within the individual grains and between separate grains.