Study on the toughening mechanism of in-situ synthesis (TixZr1−x)B2 in solid-state sintered SiC composite ceramics

Abstract

High-dense SiC-(TixZr1−x)B2 composite ceramics were fabricated by in-situ synthesis of (TixZr1−x)B2 solid solution using solid-state spark plasma sintering (SPS). 64 vol% SiC, 20 vol% ZrB2, 15 vol% TiB2, and 1 vol% graphite powders are chosen as raw materials. The composite ceramics has the relative density of 99.97 %, the Vickers hardness of 24.71 GPa, the flexure strength of 435 MPa and the fracture toughness of 8.05 MPa • m1/2. Compared with the single-phase SiC ceramics and SiC-TiB2 composite ceramics, the fracture toughness of SiC-(TixZr1−x)B2 composite ceramics increased by 242.6 % and 53.6 %, respectively. A shell-core structure is found in the SiC-(TixZr1−x)B2 composite ceramics, in which (TixZr1−x)B2 solid solution is the core and fine SiC grain is the shell. The results show that the toughening effect of solid-state sintered SiC-(TixZr1−x)B2 composite ceramics is attributed to the shell-core structure.