晶粒互锁结构与短切碳纤维增韧ZrB2-SiC复合材料的制备与力学性能

ZrB₂-SiC基复合材料具有比单体ZrB₂更优异的抗氧化性能及力学性能, 但其相对较低的韧性限制了其实际工程应用, 采用微结构设计或引入增韧相是改善陶瓷材料韧性的两个有效途径。本研究采用反应热压烧结工艺, 分别制备了具有独特片状ZrB₂晶粒互锁结构的ZrB₂-SiC复合材料和以短切碳纤维(C_sf)为增韧相的C_sf/ZrB₂-SiC复合材料。对比研究发现, 晶粒互锁结构展现出优异的自强韧化效果, 使ZrB₂-SiC复合材料具有较高的弯曲强度及断裂韧性, 但材料表现出典型的脆性断裂特征; C_sf/ZrB₂-SiC复合材料弯曲强度下降, 但C_sf具有显著的增韧作用, 不仅使材料具有较高的断裂韧性, 而且临界裂纹尺寸及断裂功都得到显著提高, 从而表现出非灾难性破坏模式。

ZrB2-SiC Composites Toughened by Interlocking Microstructure and Chopped Carbon Fiber

ZrB₂-SiC ceramics present better oxidation resistance and mechanical properties than monolithic ZrB₂ ceramics. However, the small damage tolerance and poor crack growth resistance, which result in the low fracture toughness, limit the engineering application of ZrB₂-SiC ceramics. Focusing on this issue, microstructure design and introduction of toughening phase are two effective approaches to improve the fracture toughness of ZrB₂-SiC ceramics. In this work, ZrB₂-SiC and C_f/ZrB₂-SiC composites were toughened respectively by interlocking microstructure and chopped carbon fibers via reactive hot pressing. For the ZrB₂-SiC composites, the interlocking microstructure formed by in-situ ZrB₂ platelets presented excellent self-enhancing effect. The ZrB₂-SiC composites had high bending strength and fracture toughness. However, the composite exhibited typical brittle fracture characteristics. Compared with ZrB₂-SiC composite, the flexural strength of C_f/ZrB₂-SiC composite decreased, but the fracture toughness was comparable with the ZrB₂-SiC composite. Furthermore, the critical crack size and the work of fracture of C_f/ZrB₂-SiC composites significantly improved, and the composite presented the non-catastrophic failure mode.