Abstract: Embodiments of the present invention provide composite bodies having a discontinuous graphite preform and at least one silicon-bearing metal alloy infiltrant. Embodiments of the present invention also provide methods for producing such composite bodies. The metal alloy is preferably comprised of aluminum, copper, or magnesium, or combinations thereof. Certain preferred embodiments provide at least one aluminum alloy having from about 5% silicon to about 30% silicon, more preferably from about 11% to about 13% silicon, as an alloying element. Certain presently preferred embodiments provide an aluminum-silicon eutectic composition having about 12.5% silicon. Embodiments of the invention provide composite materials be “tuned” to more closely match thermal expansion characteristics of a number of semiconductor or integrated circuit materials such as, but not limited to, silicon, alumina, aluminum nitride, gallium nitride, and gallium arsenide while also providing high thermal conductivity.