| Metal matrix composites reinforced with ceramic nanoparticles, termed as Metal Matrix Nanocomposites (MMNCs), can provide a significantly improved performance at both ambient and elevated temperatures with a low volume fraction of reinforcements.; In this research, a cost effective and reliable fabrication process, ultrasonic cavitation based solidification method is developed for high volume fabrication of MMNCs. It combines casting process with ultrasonic non-linear effects, namely transient cavitation and acoustic streaming, to produce high quality bulk Al nanocomposites. The interactions between high intensity ultrasonic non-linear effects and nanoparticles in aluminum melt were theoretically studied with a two-nanoparticle agglomeration model. The theoretical study suggested that the nanoparticles can be effectively dispersed by the transient ultrasonic cavitation effect. Al alloy A356 and spherical SiC nanoparticles were selected as the material system to form MMNCs. An experimental ultrasonic-based casting system with a niobium ultrasonic probe (4 kW) was developed to yield a casting capacity of 2 lbs. To optimize the ultrasonic processing parameters, the design of experiment (DOE) method was applied. For the Al matrix nanocomposites produced with optimized parameters, with only 1.0 wt.% SiC nanoparticles, their tensile and yield strengths were improved more than 80% while the ductility remained almost the same. The micro and nano structures of the nanocomposites were also studied with various materials characterization methods, including SEM and TEM. A nearly uniform distribution and good dispersion of nanoparticles in matrix have been achieved with a coherent interfacial bonding between the embedded SiC nanoparticles and the Al alloy matrix.; The Al MMNCs produced by the ultrasonic cavitation based solidification processing can have a significant impact on improving energy efficient of various systems for aerospace, automotive, and electronic industries. Moreover, the processing method has a great potential to be scaled up for mass production of complex structural components of MMNCs for industrial applications. |
