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1.
《Ceramics International》2019,45(16):19650-19657
BxC-TiB2-SiC ceramic composites were fabricated via reactive hot pressing using TiC, B, and Si as the raw materials. The phase transition process was studied by heating powder mixtures to different temperatures in combination with X-ray diffraction analysis. The stoichiometric ratio between B and C in boron carbide is variable. A series of powder mixtures containing excess boron (0 wt%, 10 wt%, 20 wt%, or 30 wt% B) were sintered, and the microstructures and mechanical properties of the composites were investigated. The results showed that the B6.1C-TiB2-SiC composite prepared from the starting powders with 30 wt% excess boron had the best comprehensive mechanical properties, with a relative density, hardness, bending strength, and fracture toughness of 98.32%, 33.2 GPa, 840 MPa, and 5.22 MPa m1/2, respectively. Excessive boron substitution may cause lattice distortion in boron carbide, and the boron carbide grains in this state may form a large number of twins under the compressive stress generated by the TiB2 grains, which will affect the properties of the composites. 相似文献
2.
Simone Failla Cesare Melandri Luca Zoli Guido Zucca Diletta Sciti 《Journal of the European Ceramic Society》2018,38(9):3089-3095
B4C-TiB2 composites were contaminated with WC to study the effect on densification, microstructure and properties. WC was introduced through a mild or a high energy milling with WC-6?wt%Co spheres or directly as sintering aid to 50?vol% B4C / 50?vol%TiB2 mixtures. High energy milling was very effective in improving the densification thanks to the synergistic action of WC impurities, acting as sintering aid, and size reduction of the starting TiB2-B4C powders. As a result, the sintering temperature necessary for full densification decreased to 1860?°C and both strength and hardness benefited from the microstructure refinement, 860?±?40 MPa and 28.5?±?1.4?GPa respectively. High energy milling was then adopted for producing 75?vol% B4C/25?vol% TiB2 and 25?vol% B4C/ 75vol%TiB2 mixtures. The B4C-rich composition showed the highest hardness, 32.2?±?1.8?GPa, whilst the TiB2-rich composition showed the highest value of toughness, 5.1?±?0.1?MPa?m0.5. 相似文献
3.
Shuai Wang Yangyang Deng Shuaibo Gao Mingsheng Yang Pengfei Xing 《International Journal of Applied Ceramic Technology》2020,17(6):2569-2579
B4C-TiB2-SiC composites toughened by (TiB2-SiC) agglomerates were prepared via reactive hot pressing with B4C and TiSi2 as raw materials. Phase composition, microstructure, and mechanical properties of the fabricated composites were investigated. The function of (TiB2-SiC) agglomerates was analyzed, and the strengthening and toughening mechanism were also discussed. Results indicated that some of the in situ formed TiB2 and SiC were interlocked to form special (TiB2-SiC) agglomerates in the matrix. The good comprehensive performances of 510 MPa flexural strength, 5.84 MPa·m1/2 fracture toughness, and 31.93 GPa hardness were obtained in the composites fabricated with 30 wt% TiSi2. The in situ introduced fine TiB2 and SiC grains refined the grains of B4C due to the pinning effect, which enhanced the strength. The special (TiB2-SiC) agglomerates and the existing toughening phenomena such as crack deflection, branching, and microcrack regions induced by the mismatch of thermal expansion coefficients, had cumulative effects on improving the fracture toughness. 相似文献
4.
Guangyuan Yang Zhixiao Zhang Weixing Li Xu Guo Chunyue Liu Yingjie Shi Yanming Wang Aiyang Wang Xiaoliang Zhang Xiaorong Zhang 《International Journal of Applied Ceramic Technology》2023,20(5):3267-3278
Here, cutting properties and wear mechanism of the home-made B4C-TiB2-SiC ceramic cutting tools in turning of AISI 4340 steel workpieces were studied through a combination of finite element simulation using Deform-3D software and turning experiments. Simulation results show that cutting parameters have significant effects on the main cutting force and tool temperature of the B4C-TiB2-SiC cutting tool. The optimal cutting parameters for the ceramic cutting tool are cutting speed of 300 m/min, depth of cut of .3 mm, and feed rate of .1 mm/r. Experimental results show the cutting length of the B4C-TiB2-SiC cutting tool is about 101 m, which is 21.0% and 32.9% larger than that of the home-made B4C-TiB2 ceramic cutting tool and commercially available tungsten carbide tool, indicating that the B4C-TiB2-SiC cutting tool has a desired service life. The surface roughness of the workpieces processed by the B4C-TiB2-SiC cutting tool is 2.43 µm, which is 29.4% lower than that of the workpieces processed by the B4C-TiB2 cutting tool, indicating that the B4C-TiB2-SiC cutting tool has a satisfying machining accuracy. Wear forms of the B4C-TiB2-SiC ceramic cutting tool involve craters, chipping, and flank wear, and the main wear mechanisms are abrasive, adhesive, oxidative, and diffusion wear. 相似文献
5.
Mehri Mashhadi Ehsan Taheri-NassajMaryam Mashhadi Vincenzo M. Sglavo 《Ceramics International》2011,37(8):3229-3235
The effects of Al addition on pressureless-sintering of B4C-TiB2 composites were studied. Different amounts of Al from 0% to 5 wt.% were added to B4C-TiB2 mixtures (containing up to 30 wt.% TiB2) and the samples were pressureless sintered at 2050 °C and 2150 °C under Ar atmosphere. Physical, microstructural and mechanical properties were analysed and correlated with TiB2 and Al additions and sintering temperature. Addition of Al to B4C-TiB2 results in increased shrinkage upon sintering and final relative density and lower porosity, the effect is being more evident when both Al and TiB2 are present. Fracture strength, elastic modulus and fracture toughness of 450 MPa, 500 GPa and 6.2 MPa.m1/2, respectively were measured. 相似文献
6.
《Journal of the European Ceramic Society》2020,40(8):2862-2869
B6.5C-TiB2-SiC-BN composite ceramics were prepared by a novel solid-state reaction using TiCN, B, and Si as raw materials. The final products obtained by hot pressing at 1950 °C possessed a fine microstructure, homogeneous distribution, and excellent mechanical properties. The obtained bulk B6.5C-TiB2-SiC-BN composite ceramic shows a high relative density (98.8 %). The mechanical properties of the composites are anisotropic because of the orientation growth and structural characteristics of TiB2 and h-BN grains. The values of hardness, bending strength, and fracture toughness measured along the hot-pressing direction were 19.6 GPa, 801 MPa, and 4.30 MPa m1/2, respectively, which were higher than those measured perpendicular to the hot-pressing direction. The formation of twin structures in B6.5C and SiC grains and the crack deflections induced by h-BN and TiB2 grains are beneficial for improving the mechanical properties of these composites. 相似文献
7.
《Journal of the European Ceramic Society》2017,37(2):865-869
High-performance B4C composites toughened by TiB2-SiC agglomerates were fabricated via reactive hot pressing with B4C, TiC and Si as raw materials. The TiB2-SiC composite serves as a composite toughening phase formed in the B4C matrix through an in situ reaction; its agglomerates are composed of interlocked TiB2 and SiC, which can remarkably improve the toughness of the B4C composites. The Vickers hardness, flexural strength and fracture toughness of the B4C-TiB2-SiC composite reached 35.18 ± 0.45 GPa, 567 ± 14 MPa, and 6.38 ± 0.18 MPa m1/2 respectively. The special toughening structure of the TiB2-SiC composite introduced into B4C ceramics was evaluated for the first time in this study. 相似文献
8.
S.G. HuangK. Vanmeensel O. Van der BiestJ. Vleugels 《Journal of the European Ceramic Society》2011,31(4):637-644
B4C composites with 15 and 30 vol% TiB2 were pulsed electric current sintered from B4C-TiO2-carbon black mixtures in vacuum at 2000 °C. Full densification could be realised when applying an optimized loading cycle in which the maximum load is applied after completion of the B4C-TiB2 powder synthesis, allowing degassing of volatile species. The influence of the sintering temperature on the phase constitution and microstructure during synthesis and densification was assessed from interrupted sintering cycles. The in situ conversion of TiO2 to TiB2 was a complex process in which TiO2 is initially converted to TiB2 with B2O3 as intermediate product at 1400-1700 °C. At 1900-2000 °C, B2O3 reacted with C forming B4C and CO. The B4C and TiB2 grain size in the fully densified 30 vol% TiB2 composite was 0.97 and 0.63 μm, combining a Vickers hardness of 39.3 GPa, an excellent flexural strength of 865 MPa, and modest fracture toughness of 3.0 MPa m1/2. 相似文献
9.
Shuai Wang Lamei Li Pengfei Xing Shu Yan Qi Wu Shuaibo Gao Dan Nie 《International Journal of Applied Ceramic Technology》2020,17(2):509-518
B4C composites toughened by MoB2/Mo2B5-SiC interlocking structure were prepared via reactive hot pressing with B4C and MoSi2 as raw materials. The phase composition, microstructure, and mechanical properties of the fabricated B4C 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 MoB2/Mo2B5-SiC is formed in the obtained B4C composites. The relative density, flexural strength, and fracture toughness of the B4C composites reach 99.3%, 480 MPa, and 5.2 MPa·m1/2, respectively, when the MoSi2 content is 30 wt%. The hardness is 33 GPa when the MoSi2 content is 20 wt%. The special laminar fracture of the interlocking structure of MoB2/Mo2B5-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. 相似文献
10.
《Journal of the European Ceramic Society》2014,34(5):1123-1129
B4C-SiC composites with fine grains were fabricated with hot-pressing pyrolyzed mixtures of polycarbosilane-coated B4C powder without or with the addition of Si at 1950 °C for 1 h under the pressure of 30 MPa. SiC derived from PCS promoted the densification of B4C effectively and enhanced the fracture toughness of the composites. The sinterability and mechanical properties of the composites could be further improved by the addition of Si due to the formation of liquid Si and the elimination of free carbon during sintering. The relative density, Vickers hardness and fracture toughness of the composites prepared with PCS and 8 wt% Si reached 99.1%, 33.5 GPa, and 5.57 MPa m1/2, respectively. A number of layered structures and dislocations were observed in the B4C-SiC composites. The complicated microstructure and crack bridging by homogeneously dispersed SiC grains as well as crack deflection by SiC nanoparticles may be responsible for the improvement in toughness. 相似文献
11.
Cristina Ojalvo Fernando Guiberteau Angel L. Ortiz 《Journal of the European Ceramic Society》2019,39(9):2862-2873
Toughened, super-hard B4C triplex-particulate composites were densified by spark plasma sintering with MoSi2 additives (5, 10, and 15 vol.%) at temperatures in the range 1750–1850 °C at which the reference monolithic B4C ceramics are porous. It is proved that MoSi2 is a reactive sintering additive that promotes densification by transient liquid-phase sintering, thus yielding fully-dense B4C-MoB2-SiC composites at relatively lower temperatures. Specifically, the MoSi2 first reacts at moderate temperatures (<1150 °C) with part of B4C to form MoB2, SiC, and Si. This last is a transient component that eventually melts (at ~1400 °C), contributing to densification by liquid-phase sintering, and then (at 1500–1700 °C) reacts with free C present in the B4C starting powders to form more SiC, after which densification continues by solid-state sintering. It is found that these B4C-MoB2-SiC composites are super-hard (~30 GPa), tough (~3–4 MPa m1/2), and fine-grained, a combination that renders them very appealing for structural applications. Finally, research opportunities are discussed for the future microstructural design of a novel family of toughened, ultra-hard/super-hard multi-particulate composites based on B4C plus refractory borides and carbides. 相似文献
12.
Structure and mechanical characteristics of dense ceramic composites synthesised by reactive hot pressing of TiC–B4C powder mixtures at 1800–1950°C under 30?MPa were investigated by X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM and EDX). The results show that during hot pressing solid-phase chemical reaction 2TiC?+?B4C?=?2TiB2?+?3C has occurred with final products like TiB2–TiC–C, TiB2–C or TiB2–B4C–C hetero-modulus composite formation with around one micrometer size carbon precipitates. The fracture toughness depends on the amount of graphite precipitation and has a distinct maximum K1C?=?10?MPa?m1/2 at nearly 7?vol.-% of carbon precipitate. The fracture toughness behaviour is explained by the developed model of crack propagation. Within the model, it is shown that pores (voids) and low-modulus carbon inclusions blunt the cracks and can increase ceramic toughness in some cases. 相似文献
13.
《Journal of the European Ceramic Society》2021,41(14):6952-6961
B4C–TiB2 ceramic composites were fabricated by a two-step method. First, B4C–TiB2 composite powders were synthesized from TiC–B powder mixtures at 1400 ℃, then mixed with commercial B4C powders by ball milling and the B4C–TiB2 ceramic composites were prepared by hot pressing at 1950 ℃. This two-step method not only effectively refined TiB2 grains, but also allowed the composition of the composites to be freely designed. The microstructure and mechanical properties of the composites were investigated. The results showed that the B4C–TiB2 ceramic composite with a 10 wt% TiB2 content obtained the ideal comprehensive performance, with a volume density, Vickers hardness, bending strength, and fracture toughness of 2.61 g/cm3, 35.3 GPa, 708 MPa, and 5.82 MPa m1/2, respectively. The advantages of the in-situ reaction process were fully exerted by the two-step method, which made a remarkable contribution to the excellent properties of B4C–TiB2 ceramic composites. 相似文献
14.
《Journal of the European Ceramic Society》2022,42(14):6364-6378
Micromechanics modeling was performed to study the effects of thermal residual stress, weak interphases, TiB2 volume fraction and particle size on the mechanical responses and fracture behaviors of B4C-TiB2 composites. Experimentally observed fracture behaviors including micro-cracking and crack deflection were successfully captured. The weak interphases at B4C-TiB2 boundaries and the thermal residual stress induced during cooling by the large CTE mismatch between B4C and TiB2 were identified as two major factors to promote micro-cracking that caused the enhanced progressive failure behavior. Micro-cracking was enhanced with higher TiB2 volume fraction due to higher fraction of weak interphase and material affected by thermal residual stress. Meanwhile, micro-cracking behaviors exhibited limited change with varying TiB2 particle sizes. This modeling study successfully captured the main fracture behaviors and their trends by varying micro-structures of B4C-TiB2 composites and can potentially aid microstructure design of tougher B4C-TiB2 composites in the future. 相似文献
15.
ZrB2-ZrCx composites were produced using Zr:B4C powder mixtures in the molar ratios of 3:1, 3.5:1, 4:1, and 5:1 by reactive hot pressing (RHP) at 4-7 MPa, 1200°C for 60 minutes. X-ray diffraction analyses confirmed the formation of nonstoichiometric zirconium carbide (ZrCx) with different lattice parameters and enhanced carbide formation by increasing the Zr mole fraction. An increase in applied pressure from 4 to 7 MPa was responsible for the improved relative density (RD) of 4Zr:B4C composition from 86% to 99%. Microstructural studies on Zr-rich composites showed a reduction in unreacted B4C particles and enriched elongated ZrB2 platelets. Reaction and densification mechanism in 4Zr:B4C composition were studied as a function of temperature increased from 600 to 1200°C at an applied constant pressure of 7 MPa. After 1000°C, <40 vol.% of unreacted Zr was observed during the densification process. Concurrently, low energies of carbon diffusion and carbon vacancy formation were found to enhance nonstoichiometric ZrCx formation, which was found to be responsible for the completion of the reaction. The plastic deformation of unreacted Zr was responsible for the densification of the ZrB2-ZrCx composite. The results clearly showed that the applied pressure is five times lower than the reported values. Moreover, a temperature of 1200°C was sufficient to produce dense ZrB2-ZrCx composites. The improved microhardness, flexural strength, fracture toughness, and specific wear rate were 8.2-15 GPa, 265-590 MPa, 2.82-6.33 MPa.m1/2, and 1.43-0.376 × 10−2 mm2/N, respectively. 相似文献
16.
Pavel Istomin Elena Istomina Aleksandr Nadutkin Vladislav Grass Mikhail Kaplan 《International Journal of Applied Ceramic Technology》2019,16(2):746-752
Dense Ti3SiC2-SiC, Ti4SiC3-SiC, and Ti3SiC2-Ti4SiC3-SiC ceramic composites were fabricated through carbosilicothermic reduction of TiO2 under vacuum, followed by hot pressing of the as-synthesized products under 25 MPa at 1600°C. In the reduction step, SiC either alone or in combination with elemental Si was used as a reductant. A one-third excess of SiC was added in the reaction mixtures in order to ensure the presence of approximately 30 vol.% SiC in the products of synthesis. During the hot pressing step, the samples that contained Ti3SiC2 showed better densification compared to those containing Ti4SiC3. The obtained composites exhibited the strength properties typical of coarse-grained MAX-phase ceramics. The flexural strength values of 424 and 321 MPa were achieved in Ti3SiC2-SiC, and Ti3SiC2-Ti4SiC3-SiC composites, respectively. The fracture toughness values were 5.7 MPa·m1/2. 相似文献
17.
W.S. Rubink V. Ageh H. Lide N.A. Ley M.L. Young D.T. Casem E.J. Faierson T.W. Scharf 《Journal of the European Ceramic Society》2021,41(6):3321-3332
Spark plasma sintering (SPS) was employed to consolidate powder specimens consisting of B4C and various B4C-TiB2 compositions. SPS allowed for consolidation of pure B4C, B4C-13 vol.%TiB2, and B4C-23 vol.%TiB2 composites achieving ≥99 % theoretical density without sintering additives, residual phases (e.g., graphite), and excessive grain growth due to long sintering times. Electron and x-ray microscopies determined homogeneous microstructures along with excellent distribution of TiB2 phase in both small and larger-scaled composites. An optimized B4C-23 vol.%TiB2 composite with a targeted low density of ~3.0 g/cm3 exhibited 30–35 % increased hardness, fracture toughness, and flexural bend strength compared to several commercial armor-grade ceramics, with the flexural strength being strain rate insensitive under quasistatic and dynamic loading. Mechanistic studies determined that the improvements are a result of a) no residual graphitic carbon in the composites, b) interfacial microcrack toughening due to thermal expansion coefficient differences placing the B4C matrix in compression and TiB2 phase in tension, and c) TiB2 phase aids in crack deflection thereby increasing the amount of intergranular fracture. Collectively, the addition of TiB2 serves as a toughening and strengthening phase, and scaling of SPS samples show promise for the manufacture of ceramic composites for body armor. 相似文献
18.
《Ceramics International》2022,48(6):7897-7904
High-performance B4C-PrB6 composites were prepared via hot-pressing sintering with matrix phase B4C and with 2–5 wt% Pr6O11 as additive. The effects of different sintering processes and Pr6O11 content on the microstructure and mechanical properties of the composites were studied in detail. It is found that increasing sintering temperature and pressure will contribute to the densification of B4C-PrB6 composites. Coarse grains are formed in B4C without additives at high temperature conditions, resulting in the decrease of the densification. Pr6O11 can effectively hinder the formation of coarse grains and finally promote the densification of the composites. The main toughening mechanisms of composites was crack deflection. The composites with 4 wt% Pr6O11 prepared at 2050 °C and 25 MPa had the best comprehensive mechanical properties. The relative density, hardness, flexural strength and fracture toughness reached to 98.9%, 37.6 GPa, 339 MPa and 4.4 MP am1/2, respectively. 相似文献
19.
《Journal of the European Ceramic Society》2020,40(15):5272-5285
Toughening of boron carbide (B4C) without hardness degradation, was achieved by hierarchical structures consisting of B4C micro-grains, titanium diboride (TiB2) grains, and graphitic phases along B4C grain boundaries. Such hierarchical structures were uniquely achieved by co-sintering of B4C micro-powder and carbon-rich B4C nano-powder, in situ formation of TiB2, and by utilizing the short sintering time of field-assisted sintering technology. Toughening mechanisms observed after micro-indentation include crack deflection and delamination of graphite platelets, micro-crack toughening and crack deflection/bridging by TiB2 grains. Fracture toughness enhancement was achieved while maintaining hardness: 4.65 ± 0.49 MPa m1/2 fracture toughness and 31.88 ± 1.85 GPa hardness for a micro/nano B4C-TiB2 composite (15 vol% TiB2 and 15 vol% B4C nano-powders) vs. 2.98 ± 0.24 MPa m1/2 and 32.46 ± 1.67 GPa for a reference micro B4C sample. In future, macro-scale mechanical testing will be conducted to further evaluate how these micro-scale hierarchical structures can be translated to macro-scale mechanical properties. 相似文献
20.
《Ceramics International》2022,48(9):11981-11987
Previous research have reported that B4C–TiB2 composites could be prepared by the reactive sintering of TiC–B powder mixtures. However, due to spontaneous oxidation of raw powders, using TiC–B powder mixtures with a B/TiC molar ratio of 6: 1 introduced an intermediate phase of C during the sintering process, which deteriorated the hardness of the composites. In this report, the effects of B excess on the phase composition, microstructure, and mechanical properties of B4C–TiB2 composites fabricated by reactive hot pressing TiC–B powder mixtures were investigated. XRD and Raman spectra confirmed that lattice expansion occurred in B-rich boron carbide and BxC–TiB2 (x > 4) composites were obtained. The increasing B content improved the hardness and fracture toughness but decreased the flexural strength of BxC–TiB2 (x > 4) composites. When the molar ratio of B/TiC increased from 6.6:1 to 7.8:1, the Vickers hardness and the fracture toughness of the composites were enhanced from 26.7 GPa and 4.53 MPa m1/2 to 30.4 GPa and 5.78 MPa m1/2, respectively. The improved hardness was attributed to the microstructural improvement, while the toughening mechanism was crack deflection, crack bridging and crack branching. 相似文献