Xiaorong Zhang,Zhixiao Zhang,Yuming Liu,Aiyang Wang,Shi Tian,Weimin Wang,John Wang
In this work, we systematically studied the effects of powder characteristics (B 4 C, TiC and Si powders) on the existential form of toughening phases (SiC and TiB 2 ) as well as the overall microstructure and properties of B 4 C–TiB 2 –SiC composites fabricated by reactive hot pressing. The particle size of the TiC powder plays a largely determining role in the development of novel toughening phases, the TiB 2 –SiC composite structure, that are formed in the B 4 C matrix, while the Si particle size affects the agglomerate level of the SiC phase. The TiB 2 –SiC composite structure and SiC agglomerates enhance the fracture toughness, but decrease the flexural strength . Both the microstructure and mechanical properties of B 4 C–TiB 2 –SiC composites can be effectively tuned by regulating the combinations of the particle sizes of the starting powders. The B 4 C–TiB 2 –SiC composites demonstrate flexural strength, fracture toughness and Vickers hardness in the respective range of 567–632 MPa, 5.11–6.38 MPa m 1/2 , and 34.8–35.6 GPa.
Xiaorong Zhang,Zhixiao Zhang,Weimin Wang,Junhong Shan,Hongwei Che,Jingbo Mu,Guangsuo Wang
B 4 C–TiB 2 –SiC composites toughened by composite structural toughening phases, which are the units of (TiB 2 –SiC) composite, were fabricated through reactive hot pressing with B 4 C, TiC, and Si as raw materials. The units of (TiB 2 –SiC) composite with the size of 10-20 μm are composed of interlocking TiB 2 and SiC with the size of 1-5 μm. The addition of TiC and Si can effectively promote the sintering of B 4 C ceramics. The relative densities of all the B 4 C composites with different contents of TiB 2 and SiC are close to completely dense (98.9%-99.4%), thereby resulting in superior hardness (33.1-36.2 GPa). With the increase in the content of TiB 2 and SiC, the already improved fracture toughness of the B 4 C composite continuously increases (5.3-6.5 MPa·m 1/2 ), but the flexure strength initially increases and then decreases. When cracks cross the units of the (TiB 2 –SiC) composite, the cracks deflect along the interior boundary of TiB 2 and SiC inside the units. As the crack growth path is lengthened, the crack propagation direction is changed, thereby consuming more crack extension energy. The cumulative contributions improve the fracture toughness of the B 4 C composite. Therefore, the composite structural toughening units of the (TiB 2 –SiC) composite play an important role in reinforcing the fracture toughness of the composites.
危险品化学品经营许可证（带存储）