超高温下石墨弹性极限的拐点及其孔隙率影响（英文）

Inflection and Its Porosity Effect on Elastic Limit of Graphite at Ultra-high Temperature

石墨的杨氏模量随温度升高而增大并在超高温下出现拐点，该推测至今未得到有效验证，特别是石墨的弹性极限峰值及其影响因素都是未知的。尽管三点弯曲法能够简便快捷地评价陶瓷的杨氏模量，但该方法在超高温下由于无法精确测量挠度而不再适用。本研究旨在改进三点弯曲法的基础上来测量石墨直至2000℃的杨氏模量，并探讨孔隙率对石墨超高温弹性极限的影响。结果表明：石墨随温度上升的模量的拐点温度在1700～1800℃范围内；孔隙率为16．5％的石墨，在1500℃以上具有最佳的杨氏模量，该值也反映了石墨在超高温下所具有的弹性极限。

It was supposed that the Young＇s modulus of the isostatically pressed graphite could go up with the increase of temperature until a critical value. This conjecture has not been verified yet, especially for the peak value of graphite elastic limit and the corresponding affecting factors. Although three-point bending method is effective to estimate the Young＇s modulus of ceramics, it is unavailable to be used at ultra-high temperature due to the difficulties of obtaining a precise deflection at such high temperature. This paper was to measure the varying modulus of graphite at different temperatures （up to 2 000 ℃） by the modified three-point method and investigate the effect of porosity on the elastic limit of graphite at ultra-high temperature. The results indicate that the inflection point for increasing graphite modulus with temperature occurs at 1 700-1 800 ℃, and graphite with a porosity of 16.5% possesses the optimized modulus over 1 500 ℃, representing the elastic limit of graphite at ultra-high temperature.