Interfacial structure and fracture of aluminium alloy A356–SiC particle metal matrix composite

Abstract

The interfacial structure in a SiC particle reinforced aluminium alloy matrix composite has been investigated using analytical electron microscopy. It was established that no appreciable chemical reaction takes place at either silicon/SiC particle or aluminium/SiC particle interfaces. Segregation of certain alloy elements was observed using an electron microprobe. Depletion of magnesium was found to occur at the aluminium/SiC particle interfaces. Precipitation was observed on dislocations, particularly in the region of the SiC/aluminium interface. Microcracks were found at silicon/SiC particle interfaces and their probable causes are discussed. Fracture surfaces were carefully examined using scanning electron microscopy. The results imply that the silicon–SiC bonding is more brittle than the aluminium–SiC bonding. Cracks were also found in the fracture surfaces, which suggests that intergranular separation had occurred. The fracture surface tends to exhibit a more brittle morphology in the composite when compared with that in the alloy.MST/1461