Effect of Difference in Metal Particle on Fracture Toughness of Metal Particle Dispersed Alumina Matrix Composites

Fracture behavior and fracture toughness of metal particle dispersed alumina matrix composites are investigated. Ni, Ni-5Al and CoNiCrAlY particles are used for the composites. Volume fraction of the metal particles is ranging from 5 to 20 vol%. Microstructures before and after heat exposure are observed from the surface. Vickers hardness of the composites decreases with the increase in particle volume fraction. As for the composites before heat exposure, crack propagates at alumina/metal interface when the crack reaches to the particle. After heat exposure, crack mainly passes through the oxidized particle of the composites. The fracture toughness increases with the increase in volume fraction. In the same volume fraction, heat exposed composites show lower fracture toughness than that of the composites before heat exposure due to the oxidation of the metal particle which lowers the toughening potential of plastic dissipation from the metal.