SiC晶须对Al_2O_3／TiB_2／SiC_w陶瓷刀具材料高温断裂韧性的影响

EFFECT OF SiC_w CONTENTS ON THE FRACTURE TOUGHNESS OF Al_2O_3/TiB_2/SiC_w COMPOSITE AT HIGH TEMPERATURE

研究了不同ＳｉＣ晶须含量的Ａｌ_２Ｏ_３／ＴｉＢ_２／ＳｉＣ_ｗ陶瓷刀具材料的断裂韧性随温度的变化规律。结果表明：Ａｌ_２Ｏ_３／ＴｉＢ_２／ＳｉＣ_ｗ陶瓷材料的Ｋ_（Ｉｃ）在１０００℃内随温度的升高而增大；晶须含量越高，Ｋ_（Ｉｃ）增幅越大。通过计算分析表明：随温度的升高断裂时拔出的晶须大大增多。当晶须体积含量（下同）为２０％时，Ａｌ_２Ｏ_３／ＴｉＢ_２／ＳｉＣ_ｗ陶瓷在室温时只有长径比小于２．８７的晶须在断裂时才有可能产生拔出，而在９００℃时长径比小于１０的晶须都能产生拔出。在同样温度条件下，晶须含量越高所能产生拔出的晶须增多。当晶须含量为４０％时（晶须长径比为１０），在温度大于６２０℃时能产生晶须的拔出。而当晶须含量为１８％时，只有温度大于９４０℃才能产生拔出。晶须含量越高其高温增韧效果越强。

The fracture behaviour at high temperature of Al_2O_3/TiB_2/SiC_w composites with different SiC_w contents was studied. Considerable improvement in fracture toughness was observed at high temperature. The more the SiC whiskers contained, the higher the fracture toughness improved. Results also indicate that the number of SiC_w pulled out is much more increased as the temperature increases. At room temperature, when the SiC_w aspect ratio is less than 2. 87, only whiskers can be pulled out for the composite with 20% (vol) SiC_w. But at 900℃, pull out can be achieved for the whiskers whose aspect ratio is less than 10. The toughening effect at high temperature is much more improved as the SiC_w content is increased.