β'-Sialon-BN系複合焼結体の熱衝撃破壊挙動と破壊エネルギー

概要

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Fracture energy and R-curve behavior of β'-Sialon-BN composites were investigated to elucidate the strength degradation caused by thermal shock. The fracture energy and R-curve behavior were obtained from compliance analysis on the load-displacement curves of the quasi-static fracture of 3-point bend specimen with chevron-notch. The critical temperature difference of strength degradation (ΔTe.) for the composite containing 30 mass% BN was 700 K and 900 K for Z= 1.0 and 2.0(Si_<6-2>Al_zO_zN_<8-z>) , respectively. These ΔTe results agree well with the values calculated from Hasselman's equation. The steep reduction of strength by thermal shock and the disappearance of R-curve behavior were observed on the same thermal shock temperature difference ΔT. The relationship between the ratio of effective fracture energy to elastic fracture energy (γ_<eff>/γ_i) and retained strength was found to be roughly linear. It was presumed that the residual stress from thermal shock influences the crack-face contact shielding mechanism in the composites and is a possible inhibition factor to forming of the R-curve effect.
社団法人日本セラミックス協会の論文
1996-09-01