Effect of Dynamic Microstructural Change on Deformation Behavior in Liquid-Phase-Sintered Silicon Carbide with Al2O3–Y2O3–CaO Additions

Nanocrystalline β-SiC with additions of 7 wt% Al₂O₃, 2 wt% Y₂O₃, and 1 wt% CaO was subjected to tensile deformation to study its microstructural behavior under the dynamic process. The liquid-phase-sintered body had a relative density of >97% and an average grain size of 170 nm. Tension tests were conducted at initial strain rates ranging from 2 × 10⁻⁵ to 5 × 10⁻⁴ s⁻¹, in the temperature range 1973–2023 K, in both argon and N₂ atmospheres. Although grain-boundary liquids formed by the additions vaporized concurrently with the decomposition of SiC and extensive grain growth, the maximum tensile elongation of 48% was achieved in argon. Annealing experiments under the same conditions revealed that vaporization and grain growth were both dependent on experimental time. Therefore, high strain rates suffered less from the hardening effect when cavitation damage was more severe. Testing in an N₂ atmosphere brought about crystallization of the grain-boundary phase and prevented severe vaporization; however, fracture occurred at only 8% elongation. Grain-boundary sliding was still the dominant mechanism for deformation.