Microscopic, thermal and mechanical characteristics of pressureless infiltrated SiCp/Al composites doped with silicon

Microscopic, thermal, and mechanical characteristics of pressureless infiltrated SiCp/Al composites doped with silicon were investigated by OM, XRD, TEM, relatively density examination, coefficient of thermal expansion (CTE) and thermal conductivity measuring. The results show that adding Si element in matrix can markedly reduce the CTE of composites and prevent or retard the potential for chemical reactions between the aluminum alloy and SiC. The TEM of the SiC/Al interface for the composites show that the edge of the SiC particle was severely etched by the aluminum alloy without Si and SiC/Al interface be of pyramid shape. Many needle-like Al4C3 crystals were parallel or vertically linked to the SiC surface. With the increase of Si content to 5 wt%, the edge of SiC particle with 100 nm in thickness became ambiguous, and the local area took on the shape of a saw-tooth, implying that the interfacial reaction was still present. With the further addition of Si beyond 12 wt%, the interface was clear and straight. Additionally, it can be seen that the Si crystal accompanied by high density dislocation began to precipitate from the aluminum matrix when the Si content was beyond 5 wt%. The fractography of these composites with Si content from 0 wt% to 18 wt% show the plastic deformation of the matrix of the composite with 5 wt%. With the increase of Si content to 12 wt%, the plastic feature of the composite disappears and the brittle fracture of the reinforcement is the main feature. Copyright © 2010 American Scientific Publishers.