Effects of mechanical stirring as well as continuous and sequential (discontinuous) ultrasonic treatments on the microstructure, particles distribution and mechanical properties of cast Al413–SiC np nanocomposites were studied. The results showed that both types of ultrasonic treatments greatly improved the mechanical properties and microstructural characteristics of the produced nanocomposites. Furthermore, the effects of discontinuous ultrasonic treatment were rather more pronounced than those of the continuous treatment. The improvement in the yield strength of Al413–1wt%SiCnp nanocomposites produced by mechanical stirring in comparison with that of the monolithic sample was about 7%. The improvement for the nanocomposites continuously ultrasonic treated for a single 40 min period, or discontinuously ultrasonic treated for two 20 min periods was about 74% and 94%, respectively. The improvement in the mechanical properties was associated with severe refinement of the microstructure, removal of the gas layers on the particles surfaces, effective fragmentation of the agglomerates as well as improved wettability and distribution of the reinforcing particles during solidification. Keywords: Cast Al-SiC np nanocomposite; Ultrasonic treatment; Grain refinement; Mechanical characterization; Nano structured material.
