Effects of carbon fiber/Al interface on mechanical properties of carbon-fiber-reinforced aluminum-matrix composites

Carbon-fiber (CF)-reinforced aluminum-matrix composites were prepared by spreading fibers and squeeze casting. The interface structure of CF/Al composites was examined using high-resolution transmission electron microscopy (HRTEM) and electron spectroscopy for chemical analysis (ESCA). Aluminum carbide (Al4C3) interfacial reaction products were observed to nucleate heterogeneously from carbon fibers and to grow toward the aluminum matrix in the form of lath-like crystals after heat treatment. The growth of aluminum carbide was anisotropic, since it was faster along the a- and b-axes of the basal plane than along the c-axis. Both the tensile strength and the elongation of composites decline with an increased duration of heat treatment. The results of ESCA revealed that approximately 1 pct of carbide enhanced interface bonding. However, increasing the content of brittle carbides to over 3 pct after heat treatment degraded the mechanical properties of composites.