LIQUID-EXCHANGE PROCESSING AND PROPERTIES OF SIC-AL COMPOSITES

In this paper we demonstrate a novel liquid-exchange process to replac e a secondary silicon phase in reaction-bonded siliconized silicon car bides (RBSC's) with a ductile metal reinforcement phase. When RBSC is exchanged with pure Al or Al-Si liquid, secondary phase silicon is dis solved and is substituted by Al or Al-Si alloy. The resulting composit es show improvements in fracture toughness (single-edge precracked bea m technique), with K-IC value up to 8.6 MPa . m(1/2), compared to 3-4 MPa . m(1/2) in otherwise similar siliconized silicon carbide, Increas ed fracture strength (four point flexure) was also observed after the liquid exchange process. The processing furthermore allows the coeffic ient of thermal, expansion to be adjusted, and the thermal conductivit y increased, for electronic packaging applications.