Thermal properties of aluminum–graphite composites by powder metallurgy

Abstract

10–90vol.% of flake graphite is combined with aluminum powders to form aluminum–graphite composites via vacuum hot pressing process. The results show that the relative density of powder composites achieves up to 99% for composites containing 10–90vol.% graphite. With the increase of flake graphite from 10 to 90vol.% in the composites, thermal conductivity increase from 324 to 783W/mK; the coefficients of thermal expansion (CTE) in direction parallel to basal planes of graphite flakes decrease from 16.9 to −2.5ppm/K, and the CTE perpendicular to basal plane decreases from 15.2 to 10.1ppm/K. The parallel arrangements of graphite flakes and aluminum lead the thermal conductivity values of composites to agree well with parallel model estimations. The CTE of composites in a-axis agree with rule of mixture estimation representing proportional contribution of the two phases. Along the c-axis of graphite in composites, the CTE are consistent with Turner model estimations indicating that the graphite flake could absorb the expansion from the aluminum phase.