Effect of CeO(2) Content on Microstructure and Properties of SiCp/Al-Si Composites Prepared by Powder Metallurgy

The effect of CeO(2) content on the microstructure and properties of SiCp/Al-Si composites prepared by powder metallurgy was studied, and the mechanism of CeO(2) in composites was deeply analyzed. The results show that the addition of the appropriate amount of CeO(2) can refine the Si particles and improve the tensile properties of the SiCp/Al-Si composites. As the CeO(2) content increases from 0 to 0.4 vol%, the particle size of the Si phase shows a tendency to decrease first and then increase, while the tensile strength, yield strength, and elongation of the composites show a trend of first increasing and then decreasing. When the CeO(2) content is 0.2 vol%, the refining effect of CeO(2) and the tensile properties of composites are the best. The fracture mode of SiCp/Al-Si composites with a rare earth addition is a mixed fracture. There are three main mechanisms for CeO(2) in SiCp/Al-Si composites. One is when CeO(2) serves as the nucleation substrate of Si phase to refine Si particles. The second is when CeO(2) reacts with the alloying elements in the aluminum matrix to form a new phase, CeCu(2)Si(2), which can not only play a role of dispersion strengthening, but also improve the bonding strength between Al matrix and Si particles. The third is the pinning effect of CeO(2) and CeCu(2)Si(2) particles on grain boundaries or phase boundaries to refine aluminum grains.