Microstructure and mechanical properties of AA5456/SiO2p nanocomposite fabricated by friction stir processing

Friction stir processing is a solid-state method used for local homogenization, grain structure refinement, and improvement of mechanical properties of metallic materials. Through this method, AA5456/SiO2/5-15p nanocomposites were produced in the present research. The average particle size of the reinforcements was 20 nm. The processing parameters included the constant traverse of 8 mm/min and rotational speeds of 800 and 2500 rpm. The microstructural examinations were carried out using the optical and scanning electron microscopies. The results showed that the average grain size of the stir zone reduced by incorporation of the reinforcing particles into the matrix. It was also observed that the increase in the rotational speed results in a decrease in the grain size of the stir zone. The mechanical properties of the friction stir processed composites were also evaluated by the microhardness and tensile testing. It was revealed that the microhardness is increased from 80 to 170 HV when the rotational speed increases. The tensile test results showed an improved strength from 130 to 210 MPa for samples with lower percentages of reinforcements.