Fully Dense α‐SiC Ceramics With Enhanced Strength and Toughness Fabricated by High‐Pressure Sintering

ABSTRACT In this study, single‐phase α‐SiC ceramics with full density and limited grain growth were obtained at 1850°C under 200 MPa. Transmission electron microscopy (TEM) revealed numerous microstructural defects, including stacking faults and Lomer–Cottrell locks, in the samples sintered under 200 MPa, and the dislocation density was up to 1.17 × 10 15 m −2 . High pressure promoted densification. Grain growth was suppressed by the combined effect of high pressure and a lower sintering temperature. The high pressure enhanced the mechanical properties by inducing plastic deformation that introduced numerous microstructural defects. The samples sintered under 200 MPa had the Vickers hardness of 30.18 ± 0.15 GPa, the bending strength of 571.5 ± 10.27 MPa, and the fracture toughness of 6.81 ± 0.33 MPa m 1/2 . Compared to the samples sintered under 50 MPa, the samples sintered under 200 MPa increased Vickers hardness, bending strength, and fracture toughness, respectively, by 61%, 56%, and 33%, demonstrating the significant enhancement in the strength and toughness. This enhancement effect was attributed to the limited grain growth and the high density of defects introduced by high‐pressure sintering.