FRACTURE-TOUGHNESS OF DISCONTINUOUSLY REINFORCED ALUMINUM-6061 MATRIXCOMPOSITES

The fracture toughness of two aluminium 6061 matrix composites reinfor ced with 20 vol % discontinuous reinforcement has been determined over a range of heat treatments. The materials investigated were Comral-85 , reinforced with 20 vol % alumina-based microspheres, and Duralcan re inforced with 20 vol % angular alumina particulates. These were produc ed in an identical manner. Although the fracture toughness of both mat erials was relatively insensitive to ageing time, the Duralcan composi te was significantly tougher than Comral-85 for all heat treatments ex amined. The matrix composition of both alloys was determined and it wa s found that Comral-85 contained higher additions of silicon and iron, resulting in the formation of an increased density of secondary parti cles. This was found to be the primary cause of the difference in frac ture toughness between these two materials.