Toughening of ceramics by dislocation sub-boundaries

A technique has been developed to improve the fracture toughness of sub-surface regions of ceramic materials. Surfaces of different ceramic materials (single crystals of Al2O3 and Si; sintered poly-crystals of Al2O3 and Si3N4) were impacted with hard ceramic particles at room temperature using a shot blasting technique. This treatment created a high density of tangled dislocations and micro-cracks in the sub-surface region. On subsequent annealing at high temperatures, the micro-cracks disappeared as a result of healing, while the dislocations formed well-defined sub-boundaries. This toughening technique improved the fracture toughness, KIC, by factors ranging from 1.4 to 4.0.