Study on bulk aluminum matrix nano-composite fabricated by ultrasonic dispersion of nano-sized SiC particles in molten aluminum alloy

Lightweight metal matrix nano-composites (MMNCs) (metal matrix with nano-sized ceramic particles) can be of significance for automobile, aerospace and numerous other applications. It would be advantageous to produce low-cost as-cast bulk lightweight components of MMNCs. However, it is extremely difficult to disperse nano-sized ceramic particles uniformly in molten metal. This paper presents a new method for an inexpensive fabrication of bulk lightweight MMNCs with reproducible microstructures and superior properties by use of ultrasonic nonlinear effects, namely transient cavitation and acoustic streaming, to achieve uniform dispersion of nano-sized SiC particles in molten aluminum alloy A356. Microstructural study was carried out with an optical microscope, SEM, EDS mapping, and XPS. It validates a good dispersion of nano-sized SiC in metal matrix. It also indicates that partial oxidation of SiC nanopartilces results in the formation of SiO2 in the matrix. Mechanical properties of the as-cast MMNCs have been improved significantly even with a low weight fraction of nano-sized SiC. The ultrasonic fabrication methodology is promising to produce a wide range of other MMNCs.