The effect of CeO2 content on the microstructure and properties of SiCp/Al-Si composites prepared by powder metallurgy was studied, and the mechanism of CeO2 in composites was deeply analyzed. The results show that the addition of the appropriate amount of CeO2 can refine the Si particles and improve the tensile properties of the SiCp/Al-Si composites. As the CeO2 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 CeO2 content is 0.2 vol%, the refining effect of CeO2 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 CeO2 in SiCp/Al-Si composites. One is when CeO2 serves as the nucleation substrate of Si phase to refine Si particles. The second is when CeO2 reacts with the alloying elements in the aluminum matrix to form a new phase, CeCu2Si2, 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 CeO2 and CeCu2Si2 particles on grain boundaries or phase boundaries to refine aluminum grains.
Keywords: CeO2; microstructure; powder metallurgy; tensile properties.