Effect of flake powder metallurgy on thermal conductivity of graphite flakes reinforced aluminum matrix composites

The optimization of metal-matrix composite material is linked firstly with the intrinsic properties of the matrix and the reinforcement used and secondly with the reinforcement-matrix interfacial zone and the distribution/orientation of the reinforcement inside the metal-matrix. Flake powder metallurgy was used to fabricate graphite flake reinforced aluminum matrix (Al/GF) composites fabricated by vacuum hot pressing. Two types of aluminum powders morphology were used: spherical (Al-S) and flake (Al-F) powders. A higher thermal conductivity in the in-plane direction of the graphite flakes was obtained for Al/GF composite materials fabricated with aluminum flake powder. In addition to a better orientation of the GF in the flake aluminum matrix, a 3D puckered surface and plane surface are formed at the Al/GF interface in, respectively, Al-S/GF and Al-F/GF composite materials. Due to the morphology incompatibility between the graphite flakes and the spherical powder, the damaged inner structure of GF contributes to a limited enhancement of thermal conductivity in Al-S/GF composite materials.