SiC_W对TiB_2／25SiC_W陶瓷材料高温增韧效果的影响

EFFECT OF THE SiC_W ON THE TOUGHENING BEHAVIOR OF TiB_2 / 25SiC_W CERAMIC COMPOSITE AT ELEVATED TEMPERATURE

采用热压工艺制备了ＴｉＢ２／ＳｉＣＷ陶瓷复合材料．结果表明：在ＴｉＢ２基体中添加体积分率为２５％的ＳｉＣ晶须，可显著的提高材料的断裂韧性和抗弯强度实验表明ＴｉＢ２／２５ＳｉＣＷ陶瓷材料的断裂韧性在１０００℃内随温度的升高而增大，其原因是由于温度的升高使晶须径向残余压应力松弛，晶须拔出所需要的力见减小温度越高，晶须拔出越容易，能够被拔出的晶须量增多，拔出功增大在低温下晶须以脆扯断裂为主，在高温下晶须以拔出为主。

TiB2/25SiCw ceramic composite was fabricated by hot pressing technique.Substantial improvements in fracture toughness and bending strength were obtained for the composite compared with pure TiB2 ceramic.Considerable improvement in fracture toughness at elevated temperature of TiB2/25SiCwceramic composite was observed.It was found that the SiCw numbers that can be pulled out are much more increased as the temperature increased owing to the relaxation of the residual stresses caused by the thermal expansion mismatch.At low temperature,the whiskers are mainly fractured;but at elevated temperature,the whiskers are mainly pulled out.