Experimental and Numerical Analysis of the 6061-Based Nanocomposites Fabricated via Ultrasonic Processing

There is strong evidence showing that microstructure and mechanical properties of a cast component can be considerably improved if nanoparticles are used as a reinforcement to form a metal-matrix nanocomposite. In this paper, 6061 nanocomposite castings were fabricated using the ultrasonic stirring technology (UST). The 6061 alloy and Al₂O₃/SiC nanoparticles were used as the matrix alloy and the reinforcement, respectively. Nanoparticles were injected into the molten metal and dispersed by ultrasonic cavitation and acoustic streaming. The applied UST parameters in the current experiments were used to validate a recently developed multiphase computational fluid dynamics (CFD) model, which was used to model the nanoparticle dispersion during UST processing. The CFD model accounts for turbulent fluid flow, heat transfer, and the complex interaction between the molten alloy and nanoparticles using the ANSYS’s fluent dense discrete phase model (DDPM). The modeling study includes the effects of ultrasonic probe location and the initial location where the nanoparticles are injected into the molten alloy. The microstructure, mechanical behavior, and mechanical properties of the cast nanocomposites have been also investigated in detail. The current experimental results showed that the tensile strength of the as-cast-reinforced 6061 alloy with Al₂O₃ or SiC nanoparticles increased slightly while the elongation increased significantly. The addition of the Al₂O₃ or SiC nanoparticles in 6061 alloy matrix changed the fracture mechanism from brittle dominated to ductile dominated.