The superplasticity of two kinds of aluminium alloy matrix composites was studied. One composite is a SiCp/2024 aluminium alloy matrix composites produced by a stir-cast method, while the other is a SiCp/2618 aluminium alloy matrix composite produced by a powder metallurgy method. Fracture surfaces of superplastic deformed tensile specimens were examined by SEM. It was found that there were some filaments at the fracture surfaces. The morphology of the filaments is related to deformation temperature. The morphology of the specimen surfaces was different at different deformation temperatures. At lower deformation temperatures, there were many micro-cracks in the surface, while at higher deformation temperatures; there were stripe patterns parallel to the tensile axis. It was considered that at the higher superplastic deformation temperature, a slight amount of liquid phase was present. This could have an important accommodation effect during superplastic deformation of aluminium alloy matrix composites.