FRACTURE CHARACTERISTICS OF A PARTICULATE-REINFORCED METAL-MATRIX COMPOSITE

The effect of particulates on the failure mechanism of an Al-Mg-Si all oy 6061 with 20% angular alumina particles was studied. Fracture tough ness tests were conducted on compact tension peak-aged specimens. The interaction of the reinforcement phase with the crack was investigated by optical microscopy and scanning electron microscopy, both on the s urface and in the mid-thickness of the fractured specimen. It is shown that the fractured particles ahead of the crack tip, in particular th e larger particles, play an important role in the void-initiation phas e of the fracture process. Particle size and aspect ratio determine th e likelihood of fracture. Some differences in the failure mechanisms h ave been observed between the mid-thickness and the surface of the spe cimen because of the difference between plane strain and plane stress fractures.