Abstract: SiC P/ZL109 composites fabricated by centrifugal casting and squeeze casting were characterized by conventional TEM. The leading phase Si in the (Al+Si) eutectic tended to nucleate and grow preferentially at the SiC surface(facets), thus forming the characteristic “interfacial Si” and the SiC/Si interfaces. A “subgrain Al layer” was usually observed at the Al side of a SiC/Al interface, which was less than 1μm thick with high density of dislocation generated in it. Measurements of crystallographic orientation relationship between SiC and Al and between SiC and Si were made at tens of SiC/Si and SiC/Al interfaces. ITis shown that no fixed and unique orientation relationships were determined, though the following preferential ones were observed: (1103)_SiC //(111) _Al ,1120 _SiC //110 _Al ; (1101) _SiC //(111) _Si ,1120 _SiC //112 _Si .