Effects of high pressure and SiC content on microstructure and precipitation kinetics of Al–20Si alloy

Abstract

Abstract The microstructure and the precipitation kinetics of Si in Al–20Si composites reinforced with different amounts of SiC particles are investigated as a function of the solidification pressure. The results show that the formation of primary silicon is hindered and a supersaturated dendritic α-Al phase is formed with increasing pressure. In addition, the morphology of the eutectic silicon changes from coarse acicular to short lamellar shape. After the addition of the SiC particles, the morphology of primary Si transforms from coarse polygonal to fine blocky shape, the size decreases from 72.5 μm to 11.2 μm at 1 GPa, and the eutectic Si varies from lamellar to fine fibrous structure at 3 GPa. The peak temperature and the activation energy for the Si precipitation decrease with increasing of the solidification pressure and the volume fraction of SiC. More precipitates with smaller size can be observed for high SiC contents.