Sintering Behavior of Aluminum-Graphite and its Effect on Thermal Property Using Spark Plasma Sintering Method

The spherical type of aluminum (Al) was mixed with (20, 30, 40, 50, and 60 vol.%) flake type of graphite (Gf) using a shake mixer at 2,500 rpm for 1 hr. The Al-Gf mixed powders were consolidated by spark plasma sintering under the following process conditions; sintering temperature of 480°C with heating rate of 60 °C/min, sintering pressure of 40 MPa and duration of 2 minutes at the temperature of 480°C. The results showed that the Al-20 vol.% Gf sintered-body achieved highest relative density of 98%, while the lowest value was 92% when the Gf content was 60 vol.%. The porosity rate, measured using ImageJ, ranged from 2.0 to 8.5% as the Gf content increased. The decrease in relative density was attributed to the formation of pores at the Al-Gf interface. This was due to the increased Gf content that is stable at high temperatures and the poor wettability between Al and Gf. The thermal conductivity of the composites increased from 198 to 340 W/mK as the Gf content increased. However, the thermal conductivity of the Al-60 vol.% Gf composites was 260 W/mK due to the higher porosity and orientation of Gf. In conclusion, the increase in Gf content in the Al-Gf composites led to a decrease in relative density because of pore formation. Nevertheless, the thermal conductivity of the composites generally increased with increasing Gf content, except for the Al-60 vol.% Gf composite, which exhibited lower thermal conductivity due to the higher porosity.