Effect of atmosphere on superplastic deformation behavior in nanocrystalline liquid-phase-sintered silicon carbide with Al2O3-Y2O3 additions

摘要

Nanocrystalline β-SiC with additions of 5.135 wt% Al2O3 and 3.867 wt% Y2O3 was subjected to tensile deformation in order to study its microstructural behavior under the dynamic process. The liquid-phase-sintered body had a relative density of >95% and an average grain size of 190 nm. Tension tests were conducted at initial strain rates range from 3 × 10−4 to 2 × 10−5 s−1, in the temperature range 1873–2048 K, in both argon and N2 atmospheres. Although grain-boundary liquids formed by the additions vaporized concurrently with the decomposition of SiC and grain growth, the maximum tensile elongation of 60% was achieved in argon. The grain-boundary amorphous phase formed a crystalline phase during testing in an N2 atmosphere and fracture occurred at <8% elongation. Grain-boundary sliding was still the dominant mechanism for deformation.