Effects of nano-SiCp content on microstructure and mechanical properties of SiCp/A356 composites assisted with ultrasonic treatment

nano-SiCp/A356 composites with different nano-SiCp contents were prepared by squeeze casting after ultrasonic treatment (UT). The effects of SiCp content on the microstructure and mechanical properties of the nanocomposites were investigated. The results show that with the addition of nano-SiCp, the microstructure of nanocomposites is obviously refined, the morphology of the alpha(Al) grains transforms from coarse dendrites to rosette crystals, and long acicular eutectic Si phases are shortened and rounded. The mechanical properties of 0.5%, 1% and 2% (mass fraction) SiCp/A356 nanocomposites are improved continuously with the increase of nano-SiCp content. Especially, when the SiCp content is 2%, the tensile strength, yield strength and elongation are 259 MPa, 144 MPa and 5.3%, which are increased by 19%, 69% and 15%, respectively, compared with those of the matrix alloy. The improvement of strength is attributed to mechanisms of Hall-Petch strengthening and Orowan strengthening.