Carbon nanotubes with their special properties are a suitable choice for reinforcing the metal matrix composites. In this research as cast A356-CNT nanocomposites were fabricated by means of squeeze casting method and dilution of Al-CNT composite sheets produced by continual annealing and roll-bonding process into the molten matrix alloy. The aim was to improve the wettability and distribution of CNTs in the matrix. The effects of carbon nanotubes and squeeze casting process on structural, mechanical and physical properties as well as the corrosion rate were investigated. Furthermore, mathematical relations between the inputs and outputs of the system were modeled by Design-Expert software and the optimum intervals of input parameters to obtain desired results were calculated. Results showed that structural, mechanical and physical properties of as cast nanocomposites were improved by the employed process. It was shown that grain size and secondary dendrite arm spacing were reduced whereas the ultimate shear strength and shear yield strength at room and high temperatures were improved. Reduction of density and enhancement of porosity by addition of carbon nanotubes to the structure and enhancement of density and reduction of porosity by squeeze casting were other results of this study. Squeeze cast nanocomposites retained about 85 percent of their shear strength at 300 °C while the conventionally cast monolithic alloy retained only about 58 percent of its shear strength at 300 °C. Electrical conductivity of castings was decreased by incorporation of carbon nanotubes to the structure and application of pressure during solidification. Corrosion rate was decreased by incorporation of carbon nanotubes to the structure and increased by squeeze casting process. The pressure, carbon nanotubes content and temperature to obtain optimum desired properties were calculated by the mathematical relations to be 137.56 MPa, 0.5 wt% and 666.75 °C, respectively. Key Words: A356-CNT nanocomposites, squeeze casting method, continual annealing and roll-bonding process, design of experiment, microstructure, casting quality, shear strength, electrical conductivity, corrosion rate
