Squeeze casting of particulate metal matrix composites

The interstices between alumina powder particles as reinforcement phase were infiltrated by commercial purity liquid aluminum using squeezing pressures. Different alumina particles (80 to 115 mu m) were used and different squeezing pressures (65 to 180 MPa) were applied. Fully infiltrated composites were achieved at relatively short squeezing time (25 seconds) with a relatively low squeezing pressure (150 MPa). Optical and scanning microscopy showed fairly uniform distribution of alumina particles in both longitudinal and transverse directions. By using this technique, it was able to produce composites of volume fraction of alumina particles as high as 0.675. The mechanical and wear properties of the produced composites showed significant improvements. The void percentage decreases as the pressure applied increases or as the alumina particle size becomes smaller. With increasing the squeezing pressures, the densities, hardness, toughness and wear resistance are all enhanced. The degree of enhancement of properties depends mainly on both alumina particle size and the squeezing pressures.