HIP焼結した窒化ケイ素の破壊靱性に及ぼす因子

概要

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Relationship between sintering conditions and micro-hardness on fracture toughness were examined for fully densified silicon nitride ceramics, which were capsule-HIP sintered at temperatures between 1823 and 2023 K under 60 MPa for 1 hour, Y_2O_3 and Al_2O_3 (in 6 mol% in total) were used as additives. The micro hardness and the fracture toughness of the sintered Si_3N_4 were sensitively affected by elastic deformation (E. D. ), the additive mole fraction and sintering temperatures as the following : (1) The fracture toughness was improved with increasing β phase fraction. This behavior is explained by the tangling of βphase grains. (2) The fracture toughness became also higher with rising E. D. . This relationship is opposite to what is expected by the theory of mechanical behavior. The E. D. may be applicable for estimating the degree of p grains tangling. (3) The sintering temperature was the most significant parameter to control theβphase fraction, and was 1.2 to 150 times more effective than other factors, according to a dimensionless analyses. (4) The maximum micro hardness was obtained at 50% of the β phase fraction.
1990-09-01