Influence of the weld thermal cycle on the grain structure of friction-stir joined 6061 aluminum alloy

In this work, the relationship between the thermal cycle generated during friction-stir welding (FSW) of a 6061 aluminum alloy and the resulting grain structure was studied. To this end, FSW was conducted at measured welding temperatures from 340 to 450 °C and cooling rates from 15 to 70 °C/s, and the evolved microstructures were systematically examined using electron backscatter diffraction (EBSD). In all cases, the evolution of the grain structure was governed by continuous recrystallization. At elevated temperatures, however, a competitive recovery retarded the recrystallization kinetics.