Effects of Bimodal and Monomodal SiC Particle on the Thermal Properties of SiC-Particle-Dispersed Al-Matrix Composite Fabricated by SPS

Abstract

Silicon carbide (SiC)‐particle‐dispersed‐aluminum (Al) matrix composites were fabricated in continuous solid‐liquid co‐existent state by spark plasma sintering (SPS) process from the mixture of SiC powders, Al powders and Al‐5mass%Si alloy powders. As the SiC powders, two kinds of powders, monomodal SiC powders of 109.8μm in diameter and a bimodal SiC powder mixture of 109.8μm and 14.3μm in diameter, were used. The microstructures and thermal conductivities of the composites fabricated were examined. These composites were all well consolidated by heating at a temperature range between 798K and 876K for 1.56ks during SPS process. No reaction at the interface between the SiC particle and the Al matrix was observed by scanning electron microscopy for the composites fabricated under the sintering conditions employed in the present study. The relative packing density of the monomodal composite decreased from 99.8% to 95.1% with increasing SiC volume fraction in a range of 55% and 65%, whereas that of the bimodal composite was 97% or higher than that in a SiC volume fraction range up to 70%. The thermal conductivity of the bimodal composite was higher than that of the monomodal composite in a SiC volume fraction range higher than 55%. The coefficient of thermal expansion of the composites falls in the upper line of Kerner’s model, indicating strong bonding between the SiC particle and the Al matrix in the composite.