CARBIDE FORMATION IN A CARBON-FIBER REINFORCED ALUMINUM COMPOSITE

Analytical electron microscopy has been used to investigate the crystallography and morphology of aluminium carbide which forms in a carbon-fibre reinforced aluminium alloy. It has been confirmed that the carbide has rhombohedral structure with a space group, R3m. The carbide crystals were observed to nucleate heterogeneously from carbon fibres and to grow into the aluminium matrix in the form of lath-like crystals. The crystals have their longitudinal axis parallel with the basal plane of the carbide and are aligned epitaxially with the aluminium matrix (0001)Al4C3 parallel-to (111)Al. It is suggested that the nucleation of the carbide is associated with defects on the surface of carbon fibres, that the growth of the carbide is highly anisotropic, and that it is controlled by a ledge movement mechanism.