Densification and mechanical properties of fine-grained Al2O3–ZrO2 composites consolidated by spark plasma sintering

► Preparation of full-dense (over 99%) Al2O3–ZrO2 composites (10wt% ZrO2) by spark plasma sintering. ► The Al2O3–ZrO2 composites with submicron-nano structure. ► Compared with the size of raw materials, the alumina grains had no significant growth. ► The Al2O3–ZrO2 composites with submicron-nano structure has a higher microhardness than micro-nano structure (alumina size in micro level). Alumina matrix composites containing 5 and 10wt% of ZrO2 were sintered under 100MPa pressure by spark plasma sintering process. Alumina powder with an average particle size of 600nm and yttria-stabilized zirconia with 16at% of Y2O3 and with a particle size of 40nm were used as starting materials. The influence of ZrO2 content and sintering temperature on microstructures and mechanical properties of the composites were investigated. All samples could be fully densified at a temperature lower than 1400°C. The microstructure analysis indicated that the alumina grains had no significant growth (alumina size controlled in submicron level 0.66–0.79μm), indicating that the zirconia particles provided a hindering effect on the grain growth of alumina. Vickers hardness and fracture toughness of composites increased with increasing ZrO2 content, and the samples containing 10wt% of ZrO2 had the highest Vickers hardness of 18GPa (5kg load) and fracture toughness of 5.1MPam1/2.