Dynamic Recrystallization in Similar 5182 Al/Al and Dissimilar Al/Fe Friction Stir Spot Welds

Dynamic recrystallization mechanisms have been studied after 5182 aluminum Friction Stir Spot Welding (FSSW) and dissimilar friction stir spot welding of 6016 aluminum alloy to IF-steel using EBSD measurements. Moreover, welds have been ice quenched after welding to state on the post-dynamic microstructure evolution after the tool removal. For the Al/Al welds, fine recrystallized grains of the stir zone result from a continuous dynamically recrystallization mechanism followed by a post-dynamic recovery that reduces the low angle boundary fraction in the periphery of the pin. As far as the dissimilar Al/Fe welds are concerned, steel grains of the base metal were fragmented into sub-grains in the thermomechanically affected zone. Nevertheless, recrystallized grains of the stirred zone were about three times larger than these sub-grains. In this case, the continuously recrystallized grains undergo a post-dynamic grain-growth during friction stir welding cooling. In the upper aluminum sheet, the recrystallization mechanisms are the same as in the Al/Al welds.