B_4C陶瓷的协同增韧

Multitoughening of B_4C Composite

采用热压工艺制备的B4C－35vol％TiB2复相陶瓷的断裂韧性值从单体B4C的3．6MPa.m1/2提高到6．5MPa.m1/2，引入游离碳后材料的韧性进一步提高，达7．6MPa.m1/2．显微结构观察表明，材料韧性的改善是因第二相颗粒TiB2和基体B4C之间的热膨胀系数不匹配而产生的残余应力导致的裂纹偏转和游离碳的引入产生的微裂纹协同增韧的结果．游高碳的存在削弱了界面的结合强度，在很强的残余应力的作用下，微裂纹成核并沿B4C－TiB2界面扩展．

B4C-35vol% TiB2 composite ceramics with various amounts of free carbon hot-pressed at2070℃ were studied. The incorporation of particulate TiB2 into B4C raised the toughness from3.6MPa.m1/2 to 6.5MPa.m1/2. A further increase of composite toughness up to 7.6MPa.m1/2 wasobtAlNed upon the addition of free carbon. SEM and TEM investigation revealed that the improvement of the composite toughness resulted from the multitoughening of both the crack deflectionassociated with the incorporation of TiB2 particles and the produced microcrack nucleated due tothe strong residual stress and weak interface caused by the presence of free carbon in the interfaceand propagated along B4C-TiB2 interfaces.