Effect of Processing Conditions on Microstructure and Thermal Conductivity of Hot-Extruded Aluminum/Graphite Composites

Aluminum/graphite composites have been successfully prepared by a hot-extrusion technique. The effects of processing conditions such as graphite particle size, graphite content, and extrusion temperature on extrusion behavior, microstructure, texture, and thermal conductivity have been systematically investigated. During the hot extrusion, the graphite was subjected to deformation and hence distributed along the extrusion direction in the extruded Al/graphite composites. The (00l) basal planes of the graphite were preferentially orientated along the extrusion direction. The preferred orientation of the graphite resulted in an anisotropy of thermal conductivity in the extruded samples. On the other hand, the utilization of bimodal graphite powder consisting of coarse and fine particles is beneficial to the enhancement of both relative density and thermal conductivity. Moreover, when a pressed green compact was rotated 90 degrees and then subjected to the hot extrusion, the resulting composite exhibited higher thermal conductivity due to its higher density, fewer Al/graphite interfaces, and higher orientation degree of the graphite.