LIU Longyang, CHEN Xianzhi, YU Hui, CHEN Yongjun, LUO Lijie, LI Wei, LI Jianbao

(State Key Laboratory of Marine Resource Utilization in South China Sea, College of Materials & Chemical Engineering, Hainan

University, Haikou 570228, Hainan, China)

Abstract: Al₂O₃/ZrO₂/SiC composite ceramics are fabricated by hot pressing at 1530 ºC in N₂ with Al₂O₃, 3Y-ZrO₂, SiCw (SiC whiskers)and SiCp (SiC particles) as raw materials and MgO as a sintering additive. The effects of the second milling time and the SiCw/SiCp weight ratio on the mechanical properties of the composites are investigated. The results indicate that the measurements dispersion degree of the flexural strength is decreased with the increase of the second milling time. The values of the flexural strength tend to be stable when the second milling time is 10 h. Additionally, the Vickers hardness, the flexural strength and the fracture toughness of the composites increase at first but then decrease with the SiCw/SiCp weight ratio increasing from 0/25 to 35/0. The maximum Vickers hardness (19.9 ± 0.1 GPa)and flexural strength (1314 ± 51 MPa) are achieved when the SiCw/SiCp weight ratio is 25/0. The fracture toughness can be up to 14.9 ±0.7 MPa·m^1/2 when the SiCw/SiCp weight ratio is 12.5/12.5. Improvements of the mechanical properties can be attributed to homogeneous distribution of SiCw in the matrix and the synergistic effects from several mechanisms, including phase transformation of ZrO₂, pull-out and crack bridging mechanism associated with SiCw.

Key words: Al₂O₃; ZrO₂; SiC; composite ceramics; mechanical properties