Fracture toughness of a 6061Al matrix composite reinforced with fine SiC particles

The fracture toughness of 6061Al alloy metal matrix composite reinforced with 15 vol% fine SiC particles of 600 nm in size under a high temperature over-aged condition was studied. And the toughness of the 6061Al matrix alloy and the same matrix alloy reinforced with coarse SiC particles of 9.5 μm were also measured for comparison. Fracture toughness tests were conducted on a servo-hydraulic testing machine by using three point bending specimens. The results showed that the toughness of the fine particle reinforced composite was obviously higher than that of the coarse particle reinforced composite in terms of crack initiation toughness, crack propagation energy and total absorbed energy. The mechanisms controlling the fracture toughness of the two composites reinforced with fine and coarse SiC particles were discussed based upon the measured toughness data and microstructure examinations by means of an optical microscope and a scanning electron microscope.