Properties of SiCp/6061-Al metal matrix composites prepared by infiltrating molten aluminum into ternary packing of SiC preforms

Abstract

SiC particles reinforced aluminum matrix composites (SiC_p/Al) with SiC content of more than 60%, without particle segregation for mirror substrate applications, are prepared by using the improved process. The improved process contains sintering process design, preform quality traceability, and equipment designing. The maximum SiC volume fraction of 70.4% is obtained by optimizing the selection of the following proportion: 71.4% coarse, 7.1% medium, and 21.5% fine particles. The variation of SiC volume fraction is correlated with the percentage of fine particles by using regression analysis. The preforms with the compressive strength above 10.34 MPa are prepared by sintering at 1600℃ for 2 h. Results showed that no defects in the scale of more than 10 µm are observed in the preforms. Due to the generation of a SiO₂ layer during the sintering process, the formation of Al₄C₃ phase was inhibited. As the SiC particle volume fraction increased from 65.6% to 70.4%, the bending strength increased from 483.2 MPa to 585.2 MPa. The elastic modulus also increased from 174.2 GPa to 206.1 GPa, while the coefficient of thermal expansion between 50℃ and 350℃ decreased from 11.02 × 10⁻⁶/℃ to 9.53 × 10⁻⁶/℃.