Evaluation of Thermal Properties based on the Shape of Aluminum Powder by a Spark Plasma Sintering Method

In this study, a high-melting point element, flake type graphite (Gr.), was added to aluminum (Al) to improve the latter’s thermal properties. Al with different particle shapes, spherical, irregular and flake shape, was mixed with graphite. Al–50 vol.% Gr. powders were mixed by a shaking mixer and sintered under the following process conditions; a sintering temperature of 480℃ with a heating rate of 60℃/min, a sintering pressure of 60 MPa and a duration of 2 minutes at the 480℃. The relative density of the sintered body reached its highest value of 98.7% when the shape of the Al particle was irregular. The lowest value 92.8% was obtained with flaked-shaped Al particles. Pores were formed due to the wettability at the Al and Gr. interface, which varied with the shape of the Al powder, thereby affecting the relative density. The orientation of Gr. was measured as 86%, 94%, and 92% for Al with spherical, flake, and irregular powder shapes, respectively. The orientation significantly influenced the thermal conductivity, which was measured as 342.5, 373.8, and 392.2 W/m·K for Al with spherical, flake, and irregular powder shapes, respectively. The thermal expansion was measured as 19.1, 18,8, and 18.6 × 10-6/K. The mechanical properties of the sintered bodies were studied to evaluate how the different Al shapes affect their characteristics based on the plane, considering the anisotropy of graphite.