Friction stir processing of spark plasma sintered aluminum matrix composites with bimodal micro- and nano-sized reinforcing Al2O3 particles

Spark plasma sintering (SPS) allowed to produce Al-based nanocomposites with 10% of Al2O3 particles where the ratio between nanosized and microsized particles was varied during production. The microstructural and mechanical behavior of the material after SPS was studied as a function of the reinforcement size and relative percentage. The SPSed composites were friction stir processed (FSPed), the processing forces and the heat input in the materials were analyzed. The microstructural and mechanical behavior of the processed materials is shown to be strongly dependent on the starting materials properties and on the employed processing parameters during FSP. Friction Stir Processing was feasible in the heat input range 2800-5700 J/mm. Nanosized ceramic particles acted as recrystallization sites during processing leading to the strength increase in the FSPed materials.