The microstructural evolution of friction stir welded AA6082-T6 aluminum alloy during cyclic deformation

The fatigue behavior of a thick section friction stir welded AA6082-T6 aluminum alloy was studied to compare damage mechanisms in the weld zone and the base metal. Fully reversed tension-compression strain-controlled fatigue tests were conducted to determine the cyclic stress response and stored energy to failure. Microstructure evolution during cyclic straining was followed using secondary electron imaging and electron backscatter diffraction in a scanning electron microscope. Fatigue cracking along grain boundaries and the formation of slip bands were observed to be the fatigue-induced microstructural features in the friction-stir-welded structure. In the base metal, micron-sized particles led to particle-induced cracking.