Interfacial reaction and fracture behavior of cobalt-coated Al2O3 reinforced aluminum composites

The effect of coating-fiber interfacial reaction on the tensile strength and fracture behavior of a squeeze cast 2024Al (Al–4.3wt.%Cu–1.5wt.%Mg) reinforced with Co-coated Al2O3 fiber has been investigated. The Co-coated Al2O3 fibers were exposed at various temperatures, ranging from 300 to 1000 °C, in a vacuum furnace before Al composite manufacture. At higher fiber annealing temperatures, the Co coating reacted with Al2O3 fiber to form Al9Co2 and Co2O3 phases. Substantial improvement in tensile strength and ductility of the Al composites occurred as the fiber annealing temperature increased and this was attributed to an increase in interfacial bonding strength between the coating and the fiber. In-situ fracture study and fractographic analysis of the Al composites suggested that (i) initial failure occurred by fiber cracking; and (ii) further failure included either interfacial debonding or severe matrix deformation, depending on interfacial bonding strength.