Thermal Properties of cBN Particle Dispersed Al Matrix Composites Fabricated by SPS

Abstract

cBN-particle-dispersed-aluminum (Al) matrix composites were fabricated in solid-liquid co-existent state by Spark Plasma Sintering (SPS) process from the mixture of cBN powders, Al powders and Al-5 mass% Si powders. The microstructures and thermal conductivities of the composites fabricated were examined. These composites were all well consolidated by heating at a temperature range between 798 K and 876 K for 1.56 ks during SPS process. No reaction at the interface between the cBN 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 Al/cBN composite fabricated at a pressure of 300 MPa was higher than 99 % in a volume fraction range of cBN between 35 % and 50 %. Thermal conductivity of the Al/cBN composite increased with increasing the cBN content in the composite in a volume fraction range between 35 and 45 vol%. The highest thermal conductivity was obtained for Al-45 vol% cBN composite and reached 305 W/mK. The coefficients of thermal expansion of the composites were a little higher than the theoretical values estimated by the upper line of Kerner’s model, indicating the bonding between the cBN particle and the Al matrix in the composite is weak a little.