Mechanism of particle dispersion into liquid aluminum alloys and wear resistance of composites

Abstract

Dispersion behaviors of Al₂O₃, α-SiC, β-SiC and SiO₂ particles in aluminum alloys were studied. Wear resistance of the composites containing these particles was examined. The time required for dispersion of Al₂O₃ and α-SiC particles into liquid aluminum alloys is prolonged with increasing volume fraction of the particles and decreasing particle diameter. By vacuum degassing heat treatment of the particles at 1273K, the dispersion time for Al₂O₃ shortens to some degree, and SiO₂ particles become dispersive into pure aluminum. In the first half of dispersion time, introduced particles agglomerate with liquid aluminum. Alumina particles in the agglomerates once increases in ratio and then rapidly disperse in the metal matrix through the maximum ratio during agitation. The ratio of particles in the powder phase, on the other hand, decreases with prolonged agitation. Wear resistance of the composites is improved by dispersing α-SiC 10μm or more and 7% or more in diameter and volume fraction of particles, respectively.