Low temperature enhanced ductility of friction stir processed 5083 aluminum alloy

Commercial 5083 Al rolled plates were subjected to friction stir processing (FSP) with two different processing parameters, having 430 and 850 rpm tool rotational speed with a single traverse feed rate of 90 mm/min. These FSP conditions resulted in two fine grained microstructures of 0·95 μm (430 rpm) and 2·6 μm (850 rpm). Tensile elongations were measured at a relatively low temperature of 250°C at three strain rates, and demonstrated that a decrease in grain size resulted in significantly enhanced ductility and lower forming loads. The occurrence of a relatively high value of strain rate sensitivity, m of 0·45 for a grain size of 0·95 μm, suggests the operation of superplastic deformation under these present experimental conditions.