B 4 C-TiB 2-SiC composites toughened by (TiB 2-SiC) agglomerates were prepared via reactive hot pressing with B 4 C and TiSi 2 as raw materials. Phase composition, microstructure, and mechanical properties of the fabricated composites were investigated. The function of (TiB 2-SiC) agglomerates was analyzed, and the strengthening and toughening mechanism were also discussed. Results indicated that some of the How to cite this article: Wang S, Deng Y, Gao S, Yang M, Xing P. Microstructure and mechanical property of (TiB 2-SiC) agglomerate-toughened B 4 C-TiB 2-SiC composites.
In this work, CeO2 sintering additive reinforced B4C ceramic composites were prepared by hot‐pressing reaction sintering under different processes of low temperature–long holding time (1980°C, 30 MPa, 3 h, 4 wt% CeO2) and high temperature–short holding time (2050°C, 30 MPa, .5 h, 4 wt% and 6 wt% CeO2). The effect of sintering process and CeO2 content on the microstructure and mechanical properties of B4C‐CeB6 composites were investigated. The existed impurities in the obtained composites were also analyzed. Results show that CeO2 is an active sintering additive. CeB6 is formed by the reaction between CeO2, B4C and C in sintering process. The densification of B4C ceramics is enhanced, and the grains can be refined by the formed CeB6, which promotes the strength. The thermal expansion coefficient mismatch, crack deflection, and fracture mode change caused by the in situ formed CeB6 improve the toughness. The process of low temperature–long holding time is more suitable for playing the role of CeO2 additive in sintering of B4C, under which condition the relative density, flexural strength, fracture toughness, and hardness reach 99%, 417 MPa, 5.32 MPa·m1/2, and 30.66 GPa, respectively. The impurities in the composites are the kinds of Ti‐contained, C‐O‐Mg‐Ca‐contained, C‐O‐Ca‐S‐contained, and Si‐contained impurities.
B4C–NdB6 composites were fabricated by in situ hot pressing at different temperatures (1950–2150°C) with B4C and Nd2O3 (2–4 wt%) as raw materials. The microstructure evolution of the composites with sintering temperature and Nd2O3 content was studied in detail, and the influence of pressure on the sintering of B4C with different contents of Nd2O3 was also investigated. The performance of the fabricated composites was researched and the toughening mechanism was discussed. The results indicate that Nd2O3 can react with B4C to form the thin‐sheet intermediate products (Nd(BO2)3, Nd2CO5) first, which then transform to band‐shaped NdB6. Pressure can reduce the distance of B4C and Nd2O3, accelerating the mass transfer and contributing to the formation of NdB6. NdB6 and intermediate products are first in agglomerate structure at 1950°C, and then the agglomerates are broken to form dispersive micron and submicron NdB6 at 2000°C by the synergistic function of pressure, diffusion at high temperature, and liquid phase sintering. NdB6 can enhance the densification owing to the bonding function. Excessive Nd2O3 content leads to residual pores, and excessive temperature (2150°C) results in the coarsening of phases. The coexistence of transgranular and intergranular fracture of NdB6 promote the fracture toughness.
B 4 C composites toughened by MoB 2 /Mo 2 B 5 -SiC interlocking structure were prepared via reactive hot pressing with B 4 C and MoSi 2 as raw materials. The phase composition, microstructure, and mechanical properties of the fabricated B 4 C composites were studied. The crack propagation and fracture surface were observed, and the toughening mechanism was analyzed. The results indicate that the interlocking structure of MoB 2 /Mo 2 B 5 -SiC is formed in the obtained B 4 C composites. The relative density, flexural strength, and fracture toughness of the B 4 C composites reach 99.3%, 480 MPa, and 5.2 MPa·m 1/2 , respectively, when the MoSi 2 content is 30 wt%.The hardness is 33 GPa when the MoSi 2 content is 20 wt%. The special laminar fracture of the interlocking structure of MoB 2 /Mo 2 B 5 -SiC elongates the crack extending path and thus consumes more energy of crack extension. The phenomena of crack bridging and branching and the special laminar fracture of the interlocking structure have a synergistic effect on promoting the overall fracture toughness. K E Y W O R D SB 4 C composites, hot pressing, interlocking structure, MoSi 2
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