Preparation of MgAl2O4-Coated Al2O3np and Migration of Ceramic Nanoparticles during Ultrasonic Processing of Aluminum Matrix Composites

Abstract

Composites reinforced by nano-ceramic particles typically result in the formation of clustering and a weak interface. The spatial distribution of particles and the wetting behavior remarkably affect the targeted properties. Here, a surface modification combined spatial control solution was demonstrated to prepare nanocomposites with homogeneous micro-structures. Poly-crystalline nano-MgAl2O4 particles that possess a good crystallographic orientation relationship with Al were coated on the surface of ceramic particles, and they were macro- and then microscopically dispersed in the melt by ultrasonic vibration with variable frequency. The reason this is that the acoustic pressure distributed in the Al melt can induce the acoustic streaming and cavitation. A model for calculating equilibrium particle migration velocity was proposed, based on which the distribution of particles could be controlled by adjusting the solidification rate and the size of particle clustering. The experimental results were validated by the prediction of the model. In addition, it was found that the relationship of the maximum radius angle with the contact angle was ω0=180°−θ, and ultrasonic vibration could provide enough energy for the later stage entering of particles to overcome the energy barrier.