Microstructural development of liquid-phase-sintered silicon carbide during annealing with uniaxial pressure

Abstract

β-SiC powders containing 1.1 wt.% α-SiC particles as seeds were hot-pressed at 1800 °C and then annealed at 2000 °C under 25 MPa uniaxial pressure to enhance grain growth. Microstructural development during annealing with pressure was investigated quantitatively and statistically using image analysis. The bimodal grain-thickness distribution in samples annealed with pressure was obtained due to abnormal grain growth of some grains. In situ-toughened microstructure has been developed after 3-h annealing. The grain-thickness and aspect ratio of large grains increase with annealing time, but grain growth comes mainly from increases in thickness after 3-h annealing, owing to the impingement of large gains. Typical flexural strength and fracture toughness of 4-h annealed sample were ∼500 MPa and ∼7.5 MPa m 1/2 , respectively.