B4C Content Research Articles

Synthesis and Properties of MoSi2–MoB–SiC Ceramics

MoB and SiC particulate reinforced MoSi2 matrix composites were synthesized in situ from Mo, Si, and B4C powder mixtures by self‐propagating high‐temperature synthesis (SHS). The SHS MoSi2–MoB–SiC products were vacuum hot‐pressed (HPed) at 1400°C for 90 min to fabricate high‐density (> 97.5% relative density) bulk composites. Microstructure refinement and improvements in the Vickers hardness and fracture toughness of the HPed composites were observed with increasing B4C content in the reaction mixture. The HPed composite of composition MoSi2–0.4MoB–0.1SiC exhibited grain size of 1–5 μm, Vickers hardness of 12.5 GPa, bending strength of 537 MPa, and fracture toughness of 3.8 MPa.m1/2. These excellent mechanical properties indicate that MoB and SiC particulate reinforced MoSi2 composites could be promising candidates for structural applications.

Preparation of B4C–ZrB2–SiC ternary eutectic composites by arc melting and their properties

B4C–ZrB2–SiC composites were synthesised by arc melting in Ar atmosphere using B4C, ZrB2 and β-SiC powders as starting materials. The ternary eutectic composition of 40B4C–20ZrB2–40SiC (mol-%) was first identified and a lamellar eutectic texture was observed. SiC and ZrB2 grains about 1 μm in thickness were uniformly dispersed in B4C matrix of B4C–ZrB2–SiC eutectic composite. B4C (003) and ZrB2 (100) planes were perpendicular to the growth direction. The Vickers hardness of B4C–ZrB2–SiC ternary eutectic composite was 30–34 GPa. The fracture toughness of B4C–ZrB2–SiC composite increased with the decrease of B4C content and the rise of ZrB2 content.

Reactive hot pressing and mechanical properties of B4C/Li2O–Al2O3–SiO2 composites

B4C/Li2O–Al2O3–SiO2 (B4C/LAS) composites with different B4C contents were fabricated using hot-pressing technique. Mechanical properties of the B4C/LAS composites were investigated as a function of initial B4C content. The addition of B4C deteriorated both fracture toughness and flexural strength of the composites initially. B4C/LAS composites demonstrated improved mechanical properties when initial B4C content increased to 10wt.%. XPS, XRD and TEM analyses illustrated that a chemical reaction took place between B4C and LAS matrix. The synergism of high relative density, high crystallinity and fine grain size, was responsible for improved mechanical properties of B4C/LAS composites.

Parametric optimization of wire electrical discharge machining on aluminium based composites through grey relational analysis

Wire Electrical Discharge Machining (WEDM) is an advanced machining process, which is suitable for making complex shapes in conducting materials including metal matrix composites (MMCs). In the present work, an analysis has been made to optimize the process parameters such as peak current, pulse on time, wire feed rate and wt.% of Boron Carbide (B4C) that affect the output responses, namely, kerf width (K) and surface roughness (SR), through the Grey Relational Analysis (GRA). Aluminium (6351) alloy reinforced with 5wt.% Silicon Carbide (SiC) and 0, 5, 10wt.% of B4C prepared through the stir casting process was used for the evaluation. The experimental results show that the optimal combination of process parameters were peak current of 12A, pulse on time of 100μs, wire feed rate of 6m/min and B4C content of 5wt.%. The influence of the pulse on time is found to be more in affecting the combined objective with a contribution of 96.19%. The crater formation on the machined surface of the composite at optimum condition was also examined through the Scanning Electron Microscope (SEM).

Preparation of multi-phase composite of tungsten carbide, tungsten boride and carbon by arc plasma melting: characterization of melt-cast product

Arc plasma melting of WC+B4C followed by an in situ furnace cooling produced a multi-phase composite consisting of tungsten carbide, tungsten boride and carbon. The melt-cast product was prepared in six different compositions by varying the boron carbide content (within 1–15wt%) at the charge stage. XRD, SAED and XPS characterizations of the product showed the major phases to constitute of W2B, WB, W2B5 (WB2), WC, W2C and C. Carbon was found to exist in three different forms, such as graphite, diamond / DLC and nanocrystalline diamond (C–C sp3 coordination). FESEM, TEM and BET studies revealed the surface morphology, microstructure and non-porous nature of the composites respectively. From micro Raman spectra it was evident that W2C and all tungsten boride phases were non-Raman active with 514nm radiation (Ar+ laser). Preliminary mechanical characterization of the polished composite samples (in solid forms) showed the hardness to increase with increase in B4C content (range: 1–10wt%). An extraordinary hardness of 3835±80 VHN with corresponding Young’s modulus of 695±33GPa was observed for the typical composition of WC+10wt% B4C. However, the hardness showed decreased value for 15wt% B4C added sample.

Effect of nano/micro B4C particles on the mechanical properties of aluminium metal matrix composites fabricated by ultrasonic cavitation-assisted solidification process

Lightweight aluminium metal matrix nanocomposites play a major role in automobile, aerospace and other industries. This work aimed to investigate the effect of the addition of micro- and nano-boron carbide particles to aluminium on the mechanical properties of the composites. The micro- and nanocomposites containing different weight % of B4C particles were fabricated using stir- and ultrasonic cavitation-assisted casting processes. The fabricated micro and nano B4C particle-reinforced composites were characterized using scanning electron microscopy (SEM) and an X-ray diffractometer. Tensile, hardness, impact and wear tests were carried out in order to evaluate the mechanical properties of the micro- and nanocomposites. The tensile test results showed that the properties of the samples containing up to 6% nano B4C-reinforced composites were better than the micro B4C-reinforced composites. The study also indicated that the ductility and impact energy of the nanocomposites were better than the micro B4C particle-reinforced composites. The wear resistance of the nanocomposite significantly increased when the B4C content was increased up to 8% of addition, and this increase was more pronounced than that resulting from micro B4C particle-reinforced composites.

Microstructure and Mechanical Properties of Al6061-31vol.% B4C Composites Prepared by Hot Isostatic Pressing

Fabrication of durable and usable composites with high content of B4C (up to 31vol.%) is quite challenging in several aspects including blending, cold isostatic pressing, and hot isostatic pressing (HIP), and especially the optimal HIP process is essential to achieve the metal matrix composite with desirable properties. The microstructure and mechanical properties of Al6061-31vol.% B4C with different particle sizes were investigated by scanning electron microscopy (SEM) and tensile testing, respectively. SEM analysis and quantitative measurements of the particle distribution reveal that B4C particles were uniformly distributed in the matrix without agglomeration when the HIP treatment temperature was about 580 °C, and x-ray diffraction also identified a dispersion of B4C particles as well as reaction products (AlB2 and Al3BC) in the composites. Microhardness of Al6061-31vol.% B4C composites was improved with B4C particle size, and the tensile strength of all the samples declined with an increase in B4C particle size. The contribution from different strengthening mechanisms was also discussed.

Effect of the content of B4C on microstructural evolution and wear behaviors of the laser-clad coatings fabricated on Ti6Al4V

TiNi/Ti2Ni-based composite coatings reinforced by TiC and TiB2 were produced on Ti6Al4V by laser cladding the mixture of a Ni-based alloy and different contents of B4C (0wt%, 5wt%, 15wt%, and 25wt%). The macromorphologies and microstructures of the coatings were examined through optical microscopy, X-ray diffractometry, scanning electron microscopy, and energy dispersive spectrometry. The microhardness, fracture toughness, and wear behaviors of the coatings were also investigated by using a microhardness tester and an ultra-functional wear testing machine. Results showed that the coatings were mainly composed of TiNi/Ti2Ni and TiC/TiB2 as the matrix and reinforcement particles, respectively. The phase constituents of the coatings were not influenced by addition of different contents of B4C. The microstructure of the reinforcements in the coatings presented the following evolution: hypereutectic consisting of blocky (TiC+TiB2)e eutectic and primary TiCp cellular dendrites (0wt% B4C), mixture of hypereutectic and willow-shaped (TiB2+TiC)p pseudoeutectic (5wt% B4C), and pseudoeutectic (15 and 25wt% B4C). With increasing B4C content, the volume fraction and size of the pseudoeutectic structures as well as the average microhardness of the coatings (850, 889, 969, and 1002HV0.2) were increased. By contrast, the average fracture toughness of the coatings was gradually decreased (4.47, 4.21, 4.06, and 3.85Mpam1/2) along with their wear volumes (0wt%, 5wt%, and 15wt% B4C). The increase in B4C content to 25wt% did not further reduce wear loss. The wear mechanism transformed from micro-cutting (0wt% B4C) into a combination of micro-cutting and brittle debonding (5wt% B4C) and finally led to brittle debonding (15wt% and 25wt% B4C). Coatings with suitable contents of B4C (less than 15wt%) showed excellent comprehensive mechanical properties.

Creep behavior and wear resistance of Al 5083 based hybrid composites reinforced with carbon nanotubes (CNTs) and boron carbide (B4C)

In the current research, aluminum based hybrid composite reinforced with boron carbide (B4C) and carbon nanotubes (CNTs) was produced by powder metallurgy method. creep behavior, wear resistance, surface roughness, and hardness of the samples were investigated. To prepare the samples, Al 5083 powder was milled with boron carbide particles and carbon nanotubes using planetary ball mill under argon atmosphere with ball-to-powder weight ratio of 10:1 for 5 h. Afterwards, the milled powders were formed by hot press process at 380°C and then were sintered at 585°C under argon atmosphere for 2 h. There was shown to be an increase in hardness values of composite with an increase in B4C content. The micrograph of worn surfaces indicate a delamination mechanism due to the presence of CNTs and abrasion mechanism in composite containing 10 vol.%B4C. Moreover, it was shown that increasing B4C content increases the wear resistance by 3 times under a load of 20 N and 10 times under a load of 10 N compared to CNTs-reinforced composite. surface roughness of the composite containing 5 vol.%CNT has shown to be more than other samples. The results of creep test showed that adding carbon nanotubes increases creep rate of Al 5083 alloy; however, adding B4C decreases its creep rate.

Pressureless sintering of (ZrB2–SiC–B4C) composites with (Y2O3 + Al2O3) additions

Pressureless sintering of (ZrB2–SiC–B4C) composites with (Y2O3+Al2O3) additions has been studied. The vol.% of SiC, B4C, and (Y2O3+Al2O3) was varied from (26, 24, and 16) to (5, 4, and 5) respectively. Hardness of composites has been found to decrease with a decrease in B4C content. Flexural strength has been found to increase with decreasing (Y2O3+Al2O3) content. No considerable decrease in flexural strength for composite with high vol.% of SiC, B4C, and (Y2O3+Al2O3) has been observed up to a temperature of 1500°C. By optimizing the composition a composite possessing a density of 4.64gcm−3, flexural strength of 213MPa, and Vickers hardness of 17.3GPa has been sintered. Conical shapes could be made by manual shaping and sintering. A complex yttria-alumina-silicate (YAG) layer was found to protect the composite from oxidation at high temperature of 1700°C. The composites exhibited good dimensional stability and thermal shock resistance at 2200°C in oxy-acetylene flame and at 2700°C in plasma flame. Formation of yttria stabilized zirconia embedded in the matrix of YAG has been identified on the flame exposed surfaces. The composite could be joined to itself by gas tungsten arc welding (GTAW) with a filler material containing (ZrB2–SiC–B4C–YAG). The shear strength of the weld was about 50% of the flexural strength of the parent composite.

Effects of B4C on the microstructure and phase transformation of porous SiC ceramics

Porous SiC ceramics sintered with B4C additive exhibit excellent corrosion resistance in hot acidic and basic solutions compared with traditional porous ceramic membrane supports. The effects of B4C on the density, phase composition, and microstructure of porous 6H–SiC ceramics were investigated in this study. The phase composition and microstructure of the as-prepared samples were characterized through X-ray diffraction, Raman spectrum, scanning electron microscopy, and electron probe microanalyzer equipped with wavelength dispersive spectrometry. B4C promoted the sintering of porous SiC ceramics within the temperature range of 2100–2200°C. The B4C content higher than 0.5wt% induced the phase transformation of 6H–SiC to 4H–SiC at 2200°C, resulting in the formation of large plate-like 4H–SiC grains, which significantly improved the flexural strength of the porous ceramics. The mechanisms of phase transformation and grain formation were also elucidated.

Effect of densification rate on consolidation and properties of Al7075–B4C composite powder

Hot quasi-static pressing and dynamic compaction of Al7075–B4C composite powder are studied in this work. Micron sized Al7075 and B4C particles were milled to obtain uniform dispersion of B4C reinforcing phase. Samples with relative densities up to 97.5, 99 and 100% were fabricated using gas gun, drop hammer and hot quasi-statically compactions respectively. The results showed that the increase of B4C content improved the hardness of the compacts but did not improve the compressive strength in the samples compacted by the gas gun. However, the ductility of the samples was reduced significantly. The samples compacted using the drop hammer and under hot quasi-static loading experienced ∼25 and 11% enhancement in the compressive strength respectively. The investigation indicated that the dynamic compaction using the gas gun was more successful if it is performed after quasi-static pre-compaction and under warm compaction process. It was concluded that the quasi-static pressing is the best fabrication technique to achieve the highest density, microhardness and strength.

Analysis of Cooling Curves, Microstructure and Properties of Chill Cast Al-B<sub>4</sub>C Composites

The cooling rate depends on the properties of the mold material which has significant influence on the formation of microstructure and in turn on the properties of the cast components. This work is aimed at preparing the Al-B4C composite using different chill materials by gravity die casting and recording the casting temperature during pouring and subsequent solidification to analyze the cooling rate of the casting. The effect of chilling on the microstructure and mechanical properties are determined. The cast specimens are cut and polished by standard metallographic procedure. Optical micrographs are taken at different magnification to reveal the microstructure and B4C particulate distribution. The micro hardness and tensile test results indicate that there is a significant increase in these properties with the increase in B4C content.

The design, microstructure and tensile properties of B4C particulate reinforced 6061Al neutron absorber composites

Based on the Monte Carlo Particle transport program MCNP, a novel boron carbide particulate reinforced 6061Al composite for neutron shielding (B4C/6061Al NACs) with high strength and low density was designed. The NACs with four volume fractions (10%, 20%, 30% and 40%) were successfully fabricated by vacuum hot pressing followed by hot rolling (VPHR) in atmospheric environments. The calculation results indicated that the neutron transmission ratio decreased with the increasing of B4C content and the thickness of plates. B4C particle is uniformly distributed in the matrix, exhibiting the good bonding in interface. The phases of neutron absorbers were mainly B4C and Al, and a spot of AlB2 and Al3BC. The grain of the matrix was refined and the dislocation was formed around the particles. With increasing the B4C content, the particles gathered, breakage appeared, and the tensile strength of composite first increased and then decreased. The failure mode of B4C/6061Al NACs included: the interfacial debonding and the cleavage fracture of particles.

Effect of sintering temperature and boron carbide content on the wear behavior of hot pressed diamond cutting segments

The aim of this study was to investigate the effect of sintering temperature and boron carbide content on wear behavior of diamond cutting segments. For this purpose, the segments contained 2, 5 and 10 wt.% B4C were prepared by hot pressing process carried out under a pressure of 35 MPa, at 600, 650 and 700 ?C for 3 minutes. The transverse rupture strength (TRS) of the segments was assessed using a three-point bending test. Ankara andesite stone was cut to examine the wear behavior of segments with boron carbide. Microstructure, surfaces of wear and fracture of segments were determined by scanning electron microscopy (SEM-EDS), and X-ray diffraction (XRD) analysis. As a result, the wear rate decreased significantly in the 0-5 wt.% B4C contents, while it increased in the 5-10 wt.% B4C contents. With increase in sintering temperature, the wear rate decreased due to the hard matrix.

Determination of Effect of B4C Content on Density and Tensile Strength of AA7075/ B4C Composite Produced via Powder Technology

Determination of Effect of B4C Content on Density and Tensile Strength of AA7075/ B4C Composite Produced via Powder Technology

Effect of B<sub>4</sub>C Content on Densification Behavior of SiC-B<sub>4</sub>C Ceramics

The SiC-B4C multi-phase ceramics was fabricated by gas-pressure sintering technology. The rare-earth oxide Al2O3combined with Er2O3/SiO2was served as sintering aids. The results were shown that the combination of Al2O3/Er2O3/SiO2sintering additives were effective for densification of SiC-B4C multi-phase ceramics. The influence of B4C content on the phase constitution, microstructure and densification behavior of the SiC-B4C multi-phase ceramics were detailed. The lose weight and volume shrinkage rate of SiC-B4C multi-phase ceramics had similar evolvement trend when B4C content increased. Keywords: Gas-Pressure Sintering, SiC-B4C multi-phase ceramics, densification behavior.

Prediction of the influence of processing parameters on synthesis of Al2024-B4C composite powders in a planetary mill using an artificial neural network

AbstractIn this study, an artificial neural network approach was employed to predict the effect of B4C size, B4C content, and milling time on the particle size and particle hardness of Al2024-B4C composite powders. Al2024-B4C powder mixtures with various reinforcement weight percentages (5%, 10%, and 20% B4C), reinforcement size (49 and 5 μm), and milling times (0–10 h) were prepared by mechanical alloying process. The properties of the composite powders were analyzed using a laser particle size analyzer for the particle size and a microhardness tester for the powder microhardness. The three input parameters in the proposed artificial neural network (ANN) were the reinforcement size, reinforcement ratio, and milling time. Particle size and particle hardness of the composite powders were the outputs obtained from the proposed ANN. The mean absolute percentage error for the predicted values did not exceed 4.289% for the best prediction model. This model can be used for predicting properties of Al2024-B4C composite powders produced with different reinforcement size, reinforcement ratio, and milling times.

Preparation and Characterization of Reaction Sintering B<sub>4</sub>C/SiC Composite Ceramic

High hardness, high strength, high fracture toughness and low density are required for novel bulletproof materials. B4C/SiC composite ceramic is one of the most potential candidates. In this study, B4C/SiC composite ceramic was prepared by reaction sintering. The influence of B4C content, species and content of carbon, sintering temperature on the mechanical properties of B4C/SiC composite ceramic were studied. A high performance B4C/SiC composite ceramic was sintered at 1750°C for 30 min. Phenolic resin and carbon black were both chosen as carbon sources, whose favorable contents were 10wt%, 5wt%, respectively. The density of sintered bodies reduces with B4C content increases. To some extent, fracture toughness, bending strength improve initially and then deteriorate with the increase of B4C content whose optimal amount is 30wt%. The optimal fracture toughness and bending strength of the B4C/SiC composite ceramic are 5.07MPa·m1/2 and 487MPa, respectively. Meanwhile, the Viker-hardness of the sintered body is 30.2GPa, the density is as low as 2.82g/cm3.

Effects of Boron Carbide Content on the Microstructure and Properties of Atmospheric Plasma-Sprayed NiCoCrAlY/Al2O3-B4C Composite Coatings

NiCoCrAlY/Al2O3 and NiCoCrAlY/B4C composite powders were prepared with hydrogen reduction and solid state alloying process. NiCoCrAlY/Al2O3-B4C composite coatings with different contents of B4C were prepared by atmospheric plasma spray technology. The microstructures, mechanical properties, and tribological properties of the composite coatings with different B4C contents were systematically investigated. The results show that the microhardness of the composite coatings increases, while the tensile strength of the composite coatings decreases, with the increase of B4C contents. The wear volume of the composite coatings decreases from room temperature to 800 °C with the increase of B4C contents. Abrasion wear is the main wear mechanism of the NiCoCrAlY/Al2O3-B4C composite coating from room temperature to 800 °C.