Papers by Keyword: B4C

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Authors: Kerim Emre Öksüz
Abstract: Increasing density is the best way to increase the performance of powder metallurgy materials. Conventional powder metallurgy processing can produce copper green compacts with density less than 8.3g/cm3 (a relative density of 93%). Warm compaction, which is a simple and economical forming process to prepare high density powder metallurgy parts or materials. CuSn matrix composites with %2 weight fractions of reinforcement particles were prepared using warm compaction and sintering. Micro-structural aspects were observed by optical microscope. Density, hardness and wear tests were also performed. Abrasion resistance measurements were used to study the abrasive behaviors of CuSn matrix and its composites. The effects of reinforcement and preparation methods on the microstructure and mechanical properties of composites have been investigated.
Authors: Rong Zhen Liu, Qing Wen Duan, Wen Wei Gu, Hai Yun Jin, Shao Chun Xu, Jian Feng Yang
Abstract: Silicon was infiltrated into B4C preforms to fabricate B4C based composites ceramics at 1600 °C under vacuum circumstance. In this paper, silicon infiltration process was discussed by theoretical calculation. The volume expansion caused by reactions between silicon and boron carbide was about 89.1% from the calculation. In our study, the maximum density of B4C preform for the infiltration of silicon was about 1.5g/cm3 which was larger than theoretical result. The results of mechanical behavior showed that B4C based composites had excellent mechanical properties with a density lower than 2.6g/cm3, Vickers-hardness of this material was 27.2GPa, and this material showed a flexural strength of 349MPa and fracture toughness of 3.8 MPa*m1/2.
Authors: Ali Arslan Kaya, E.S. Kayali, Dan Eliezer, G. Gertsberg, N. Moscovitch
Abstract: The dry sliding wear behavior of magnesium-matrix-composites (MMC) reinforced by boron carbide particulates (B4Cp) has been investigated. Magnesium is the lightest structural material and is a good choice as a metal matrix for boron carbide and silicon carbide addition. Magnesium and its alloys, without reinforcement, are generally not suitable for mechanical applications due to their low wear resistance. The MMCs used in this study were produced via highpressure die-casting technique. The wear resistance of B4C/AZ91D composite reinforced with 12 and 25 wt% B4C were studied, compared with unreinforced diecast AZ91D. As-cast microstructures of the materials and boron carbide particules were characterized by using Scanning Electron Microscopy (SEM). The hardness values of the control sample and the composites were determined via Vickers hardness measurements. Pin on disk dry sliding wear tests were carried out to study wear rate and wear mechanisms. The magnesium matrix composites were used as pins while mild steel as disc material. The worn surfaces of pins were examined by using SEM. The wear performance of magnesium matrix composites was improved with increasing volume fraction of B4C up to a certain level.
Authors: Zhi Qiang Shen, Qing Kang, Jun Xu, Zheng Gang Wang, You Jun Zeng
Abstract: Cement-based material samples having 0%, 5%, 10% and 20% B4C concentrations have been prepared for this reserach. Neutron attenuation measurement has been done by using 14.8MeV neutrons from the 5SDH-2 accelerator, and some mechanics properties of the same proportion also have been tested. It has been shown that when the B4C precentage and thickness of the samples increase, neutron attenuation values of the samples increase. Both the flexural and compressive strength firstly increased with B4C addition up to 10% approximately, and then decreased sharply with an addition up to 20%. It is thus possible to enhance the neutron shielding property of cement-based materials by adding B4C.
Authors: Bin Hao, Ji Shan Zhang, Da Cheng Liu
Abstract: In the present investigation, the composite powder with 20wt.% particulate B4C and 80wt.% nanocrystalline 5083 Al was fabricated using mechanically milling at cryogenic temperature (cryomilling). After this, the cryomilled composite powder was homogeneously blended with an equal amount of unmilled coarse-grained 5083 Al. The blended powder was consolidated with hot-pressing at 500°C, followed by hot extrusion at 410°C. The consolidated composite consists of 10wt.% B4C, 50wt.% coarse grain 5083 Al and the balance nanocrystalline 5083 Al. The microstructure evolution of the composite during cryomilling and consolidation was investigated by X-ray diffraction (XRD), optical microscopy (OM) and scanning electron microscopy (SEM). The results show that the particle size of the cryomilled composite powder became smaller and then bigger with milling time longer. This demonstrates the course rely mainly on broken first, and then rely mainly on cold welding with milling time longer. B4C particles can be distributed in 5083 Al matrix uniformly. In addition, the presence of oxygen and nitrogen in cryomilled powders has been demonstrated in this paper.
Authors: Ying Ying Liu, Ying Jie Qiao, Ai Dong Liu, Yan Wang
Abstract: The binder system removal was studied in a laminated B4C ceramics prepared by tape casting and lamination with castor oil, polyvinyl butyral(PVB) and di-n-butyl phthalate (DBP) as dispersant, binder and plasticizer, respectively. Thermo gravimetric analysis and Fourier transform infrared spectromer was used to examine the degradation of the binder system. The degradation behavior of the pure organics, single sheet and laminated B4C body were investigated. The results indicate that nitrog4en was selected as the binder system removal atmosphere and two decomposition temperature ranges was obtained for organics. A model based on diffusion can be used to predict the binder system removal time for a certain thickness of laminated B4C.
Authors: Xuan Liu, Qiang Xu, Shi Zhen Zhu
Abstract: ZrB2-SiC-B4C is sintered at 1700°C by spark plasma sintering process. The effect of B4C content on the mechanical properties and microstructure of ZrB2-SiC based ceramics is studied. The results show that, with the content of B4C increases, the relative density and room-temperature strength decrease in the ZrB2-SiC-B4C composite. The fracture toughness rises at first and then falls down. The high temperature strength increases.
Authors: Rosa Maria da Rocha, Francisco Cristóvão Lourenço de Melo
Abstract: This paper presents results of experiments on pressureless sintering of boron carbide (B4C) with addition of titânia (TiO2) and titanium diboride (TiB2). The TiB2 powder was added as a second phase and the TiO2 powder for reactive sintering and in-situ formation of TiB2. The final concentrations of TiB2 in the composites were 0 to 10 vol%. Sintering was performed at 2050 °C/30min in argon atmosphere. TiO2 was completely transformed into TiB2 with fine equiaxed grains distributed homogeneously. Composites obtained by in-situ reaction showed a densification increase with the concentration increase, while the composites with TiB2 powder mixture showed low densification in all compositions. Relative Density of the composite with 10 vol% of TiB2 obtained in-situ was 91% (TD) compared to 86 % for B4C only. Vickers hardness was about 29 GPa.
Authors: Xian Feng Li, Bin Liu, Wen Mao Huang, Hao Wei Wang
Abstract: Particles size grading method was employed to fabricate aluminum matrix composites reinforced with 75% volume fraction B4C particles by squeeze casting. Dynamic behaviors of the composite was investigated and compared with 55 vol. % composite which were reinforced with particles of uniform size. The results showed that the flow stress increased but the fracture strain decreased with increasing reinforcement volume fraction. Furthermore, the dynamic behaviors of 55 vol. % composite were significantly affected by adiabatic heating softening which was demonstrated by the local melted matrix on the fracture surface and an increase-decrease tendency on flow stress and failure strain was obtained with increasing impact velocity. However, due to load redistribution caused by particles size grading, no melted region was found on the fracture surface and no increase-decrease tendency on flow stress and failure strain was observed for 75 vol. % composites under the same impact loading.
Authors: Zhang Jian Zhou, Chang Chun Ge
Abstract: B4C is a promising candidate for using as plasma-facing material in fusion devices. In this paper, both B4C/Cu coating FGM (Funetionally graded material) and B4C/Cu bulk FGM containing a spectrum of 0-100% compositional distributions of B4C were fabricated by atmosphere plasma spray and ultra-high pressure consolidation respectively. The microstructure of B4C/Cu FGM showed good graded composition distribution. Water quenching and high heat loading experiments using an electron beam were carried out to evaluate the high heat load resistance of B4C/Cu FGMs. The in situ plasma irradiation in a Tokamak facility showed that the B4C/Cu bulk FGM has higher physical sputtering performance than that of B4C/Cu coating FGM.
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