Effect of Initial α‐Phase Content on Microstructure and Mechanical Properties of Sintered Silicon Carbide

TLDR

The study examined how varying initial α‑phase content in α‑ and β‑SiC powders affects the microstructure and mechanical properties of liquid‑phase‑sintered and annealed silicon carbide. The authors performed liquid‑phase sintering of α‑ and β‑SiC powders with similar particle sizes, annealed the samples, and analyzed the resulting microstructures by image analysis. Increasing α‑SiC content reduced grain size, maximized aspect ratio at 10 % α‑SiC, and improved strength while decreasing fracture toughness, indicating a trade‑off between strength and toughness.

Abstract

By using α‐ and β‐SiC starting powders with similar particle sizes, the effects of initial α‐phase content on the microstructure and the mechanical properties of the liquid‐phase‐sintered and subsequently annealed materials were investigated. The microstructures developed were analyzed by image analysis. When β‐SiC powder was used, the grains became elongated. The average diameter decreased with increasing α‐SiC content and the aspect ratio showed a maximum at 10%α‐SiC and decreased with increasing α‐SiC content in the starting powder. Such results suggest that microstructure can be controlled by changing α‐phase content in starting powders. The strength increased with increasing α‐SiC content in the starting powder while the fracture toughness decreased with increasing α‐SiC content. There may be a trade‐off in improving both the strength and toughness in SiC ceramics sintered with oxide additives.