MICROMECHANISM OF FRACTURE IN AL SIC COMPOSITES/

An SEM study was made of the micromechanism of fracture in SiC particl e-reinforced 6061 aluminium composites. The fracture toughness tests o n the composites with SiC volume fractions of 0%, 10% and 20% were con ducted on single-edge notched sheet specimens. Both qualitative observ ations of void nucleation at the notch root of the composite samples a nd quantitative measurements of crack profiles are made to assess the special role of the particle effects in these composites. The results are discussed with respect to the micromechanism of particle breakage and interface debonding and their effect on the nucleation and propaga tion of microcracks. Two kinds of void are defined to explain the fact s that Al/SiC is brittle macroscopically and ductile microscopically. The direction of crack propagation in Al/SiC and the microstructure in the tip region of the crack are also studied with these results.