Toughening ceramics by adding two toughening agents

The applications of ceramics for structural components are often limited by their brittleness. The toughness of ceramics can be improved by adding one toughening agent, such as zirconia particles or metallic particles. The present study explores the toughening behavior of the composites containing two toughening agents. Our results suggest that the toughness of ceramics can also be improved significantly by adding both zirconia particles and metallic inclusions simultaneous. In the present study, both metallic (silver or nickel) inclusions and zirconia inclusions are added into alumina. The processing design, microstructural evolution and the mechanical properties of the Al2O3-ZrO2-Ag and Al2O3-ZrO2-Ni composites are addressed. The metallic inclusions can bridge an advancing crack and exert crack closure stresses on the crack wake. The toughness of alumina can also be enhanced by the phase transformation of zirconia, Furthermore, the presence of the metallic inclusions increases the phase transformation extent of the zirconia particles, indicating that the toughening effect provided by the zirconia and metallic inclusions can interact with each other. Therefore, a synergy effect; namely, the toughness increase for the composites containing both ceramic particles and metallic inclusions is higher than the additive of the toughness increase of the composites containing only one reinforcement, is observed.