Microstructural evolution of the thermomechanically affected zone in a Ti–6Al–4V friction stir welded joint

Microstructural evolution of the thermomechanically affected zone (TMAZ) in a friction stir welded Ti–6Al–4V joint was investigated by electron backscattered diffraction and transmission electron microscopy. The TMAZ showed the lowest hardness in the friction stir welded sample. By comparing microstructural details of the TMAZ, including texture, misorientation angle distribution and grain structure, with those of the base material, we propose a new grain refinement model associated with continuous dynamic recrystallization and grooving in the TMAZ.