常温および高温における常圧焼結窒化ケイ素の引張強度

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A new testing device was developed to study the tensile properties of sintered silicon nitride plate specimens at room and elevated temperatures. An infrared image furnace was used to heat a specimen, and tensile tests were performed at room temperature, 1 000, 1 200 and 1 300℃. Ten specimens were used at each temperature with the purpose of statistical analysis. It was observed that the tensile strength decreased gradually when the temperature was raised from room temperature to 1 000℃, and decreased rapidly when the temperature exceeded 1 000℃. The Weibull shape parameter was in the range from 11. 9 to 16.6 with an average 14.2 for the above test temperature range. At 1 300℃, inelastic deformation caused by the viscosity drop of the glassy phase was observed on the load-displacement curve. Mirror-mist-hackle features were clearly observed on the fracture surfaces of specimens tested at room temperature, 1 000 and 1 200℃. The mirror and mist areas around the fracture origin were determined for each fractured specimen, and it was confirmed that the relation σ_B ・ r^<l/2>=const. holds between the mirror or mist radius r and the tensile strengthσ_B in the temperature range from room temperature to 1 200℃. But at 1 300℃, the fracture surface was dominated by fiat and smooth region, and it was difficult to define the mirror and mist areas. Furthermore, a slow crack growth region surrounding the fracture origin was observed on some of the fracture surfaces at 1 200 and 1 300℃.
社団法人日本材料学会の論文
1987-06-15

常温および高温における常圧焼結窒化ケイ素の引張強度

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