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.
Highlights
Aluminum metal matrix composites reinforced by ceramic particles have emerged as an important structural material for using in the automotive and aerospace industries due to their high specific strength, high-temperature creep resistance, and excellent wear resistance [1,2,3]
A recent review reported that the surface modification of reinforcements was considered to be effective in promoting particle distribution and improving the wetting behavior [5]
The aim of this study is to realize control of the size and distribution of nanoparticles in the matrix in order to make the composites with high-performance more possible, based on the studies on the influences of particle wetting and ultrasonic vibration on nanoparticle completely entering the melt and dispersion mechanism, and to establish a model of particle migration under ultrasound treatment
Summary
Aluminum metal matrix composites reinforced by ceramic particles have emerged as an important structural material for using in the automotive and aerospace industries due to their high specific strength, high-temperature creep resistance, and excellent wear resistance [1,2,3]. It is a challenging to well disperse and uniformly distribute the nanoparticles in the melts since they have larger specific surface area and poor wettability between ceramic phase and matrix alloy [3], which limits the strengthening effect of composites. MgAl2 O4 spinel was used as reinforcements in lightweight alloys because of their important properties such as low density, high strength, high melting point, and thermal shock resistance [6,7].
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