Friction Stir Processing of Aluminum Alloy A206: Part IMicrostructure Evolution

Friction stir processing (FSP) was applied to plates of cast aluminum A206 alloy. The focus of the work was on the evolution of microstructure during processing, which yielded dramatic decrease in the local grain size of the processed material. Reduction in pore morphology features, as well as intermetallic particle size, was also observed. Friction-stir-processed metal is characterized by a high ratio of high-angle grain boundaries to low-angle boundaries compared to what is observed in the as-cast alloy. Consistent with findings of other investigators, FSP generates a product nugget which has a portion of its structure having an onion skin-type structure that is characterized by a preferred crystallographic texture within individual bands in the nugget.