Dynamic fracture toughness of 6061Al composites reinforced with SiC particulates

Dynamic fracture toughness experiments were conducted at room temperature on 6061Al alloy reinforced with 15 and 25% volume fractions of 9.5μm SiC particulates. The fracture properties were evaluated in terms of crack initiation toughness, crack propagation energy and total absorbed energy. The dynamic fracture of the unreinforced 6061Al alloy was also studied as a comparison. The results of dynamic tests for both composites and matrix alloy are compared with their respective quasi-static cases. It is found that addition of SiC particles can drastically decrease fracture toughness of 6061Al alloy at both quasi-static and dynamic loading rates. 15%SiCP composite shows a considerable increase in crack initiation toughness and a much greater increment of crack propagation energy in dynamic loading case compared with static loading case, whereas 25%SiCP composite exhibits a negligible increment of crack propagation energy and a reduced increase of crack initiation energy in dynamic case in contrast to 15%SiCP composite. Detailed SEM examination of the fracture surfaces and optical observation of microstructures beneath the fracture surfaces of both composites, combined with an in-situ SEM observation, were made to investigate the fracture processes of the composites.