Investigation on texture evolution during friction stir welding of stainless steel

A two-dimensional Eulerian finite-element formulation is Used to model the motion, thermal response, and strain hardening during friction stir welding (FSW) of a stainless steel alloy. Texture evolution is predicted from the computed velocity gradients along streamlines of the flow field. The texture is assumed to be uniform initially and shows monoclinic sample symmetry after deformation. Upstream and downstream of the tool, the deformation is nearly monotonic, causing little change of the texture. Around the tool pin, the texture strengthens, weakens, and restrengthens repeatedly and rapidly. The repeated strengthening and weakening of the texture are explained with the aid of an idealized, circular streamline path and consideration of the relative magnitudes of the deformation rate and spin along the streamline.