The role of residual stress on the mechanical properties of Al 2O 3-5 vol% SiC nano-composites

Abstract

The role of nano-sized SiC particles in Al 2O 3-5 vol% SiC nano-composites is still a topical subject. As yet there is little agreement on the mechanisms of mechanical property enhancement in such composites. However, the significance of the residual stresses generated by the thermal expansion mismatch between the matrix and SiC in the composites is generally appreciated. The large shear stress generated plays a dominant role in the generation and movement of dislocations, especially during thermal treatment. It is possible that dislocation movement could also result in the microcrack healing, which contributes to the strength enhancement. The high value of the tensile residual hoop stress in the matrix is the major contribution to the transgranular fracture in the composites. The high compressive radial residual stress in the matrix contributes both to crack pinning and also crack bridging to enhance the strength and toughness. Both the radial and hoop residual stresses can help crack deflection.