Addition Of B4C Research Articles

Chemical origins of β-Ti stabilization via B4C additions in metastable β-Ti alloys and composites

The aerospace industry relies on Ti alloys owing to their strength-to-weight ratio and corrosion resistance. In metastable β-Ti alloys, slow cooling from the β-transus leads to partial transformation into coarse α laths, which is detrimental to the mechanical properties. A refinement and decrease of α laths has been previously achieved in β-Ti alloys with B4C additions. In these materials, the ductility of β-Ti is preserved, and the TiB and TiC particles promote strengthening. However, the mechanism of the β-Ti stabilization remains unclear. Using atom probe tomography, we propose that Mo enrichment in the α-phase limits its growth by reducing the influx of Al from the β-phase. The complex chemical environment near eutectic TiB is enriched in Al and TiO, promoting heterogeneous nucleation of fine α-phase. Increased TiO concentration is observed with the introduction of B4C. A fundamental understanding of the α-refinement mechanism in Ti-alloys is critical for aerospace applications demanding high performance and reliability.

The structural and mechanical properties of open-cell aluminum foams: Dependency on porosity, pore size, and ceramic particle addition

Aluminum foams are desired for lightweight, high-performance, and cost-effective materials, particularly in automotive, aerospace, and advanced power plants. Expansion of their applications depends on developing a detailed understanding of the structural and mechanical properties of aluminum foams. In this research, open-cell aluminum foams with 25.51–81.88 % porosity were manufactured through powder metallurgy using a space holder technique, with varying carbamide (urea) ratios (17–80 %) and particle sizes (1–1.4 mm, 1.7–2 mm, 2–2.4 mm). Three different ceramic particles, B4C, Al2O3, and SiC were used as reinforcement to improve the compression properties and energy absorption capacity of the foam materials. The study determined open and closed porosity ratios, spherical diameter, sphericity values, micropore sizes, mechanical properties, and energy absorption capacity of the foam samples both with and without ceramic additives. The results show that porosity ratio, pore size, and ceramic particle addition significantly affect aluminum foams' structural and mechanical properties, allowing for tailored properties for specific applications. It was observed that as porosity increased, compressive stress decreased, and the length of the plateau region and the shape change where densification began increased. However, there was no significant change in compressive stress and specific energy values with changing pore size. The optimal B4C addition was found to be 4 %, which significantly improved compressive strength to 3.75 MPa and specific energy to 4.24 MJ m−3.

Improved flux pinning properties of Mg exceed MgB2 ceramics with B4C and Dy2O3 additions

In this study, MgB2 polycrystals were synthesized via the addition of B4C and Dy2O3. X-ray diffraction confirmed that MgB2 was the predominant phase in all the samples. The superconducting properties of the samples were characterized by in-field temperature-dependent resistivity and magnetization measurements. The upper critical field (Hc2) and the critical current density (Jc) of each sample were estimated. The results indicate significant enhancements in Hc2 and Jc with the optimal addition levels of B4C and Dy2O3. According to collective pinning theory, δl pinning was identified as the dominant pinning type in the fabricated samples. The dominant pinning mechanism was determined to be core surface pinning induced by grain boundaries, which is consistent with predictions made by the Dew–Hughes model.

Microstructure evolution and high-temperature oxidation behavior of low-carbon MgO-C refractories with TiB2 addition

Combining the advantages of both containing-B compounds and containing-Ti compounds, a new TiB2 addition is proposed in MgO-C refractories. In this paper, the high-temperature oxidation behavior of low-carbon MgO-C refractories with TiB2 addition was investigated, especially the effect of microstructure and phase evolution on the high-temperature oxidation behavior was discussed. The results show that in the materials, TiB2 preferentially reacts with oxygen, forming TiCxN1-x, Mg3(BO3)2 and Mg2TiO4 ceramic phases, and catalyzing the decomposition of phenolic resin to form bamboo-like nanotubes and carbon nanospheres to bond aggregates and fill pores. Meanwhile, TiB2 also promotes the formation of regenerated MgO compact zone, hindering the diffusion of oxygen into the materials to improve the oxidation resistance. Compared with the blank control specimen and the specimen with B4C addition, the oxidation resistance increased by 243.4 % and 79.2 %, respectively.

The Influence of Adding B4C and CeO2 on the Mechanical Properties of Laser Cladding Nickel-Based Coatings on the Surface of TC4 Titanium Alloy.

The development of titanium alloys is limited by issues such as low hardness, poor wear resistance, and sensitivity to adhesive wear. Using laser cladding technology to create high-hardness wear-resistant coatings on the surface of titanium alloys is an economical and efficient method that can enhance their surface hardness and wear resistance. This paper presents the preparation of two types of nickel-based composite coatings, Ni60-Ti-Cu-xB4C and Ni60-Ti-Cu-B4C-xCeO2, on the surface of TC4 titanium alloy using laser cladding. When the B4C addition was 8 wt.%, the hardness of the cladding layer was the highest, with an average microhardness of 1078 HV, which was 3.37 times that of the TC4 substrate. The friction coefficient was reduced by 24.7% compared to the TC4 substrate, and the wear volume was only 2.7% of that of the substrate material. When the CeO2 content was 3 wt.%, the hardness of the cladding layer was the highest, with an average microhardness of 1105 HV, which was 3.45 times that of the TC4 substrate. The friction coefficient was reduced by 33.7% compared to the substrate material, and the wear volume was only 1.8% of that of the substrate material.

Investigation of Drilling Performances, Tribological and Mechanical Behaviors of GFRC Filled with B4C and Gr

AbstractIn this study, the effects of Gr and B4C filler materials on drilling performance, mechanical, and tribological behaviors of glass fiber-reinforced epoxy composites were experimentally investigated. Glass fiber-reinforced composite materials filled with B4C and Gr at different weight ratios (5%, 10%, and 15%) were manufactured using hand lay-up method. The produced composite materials underwent various tests, including mechanical tests (tensile and flexural tests), tribological tests (wear behavior), and drilling tests under different parameters. Additionally, SEM images of the worn and fractured surfaces were examined. The addition of both B4C and Gr fillers adversely affected the mechanical properties of glass fiber-reinforced composites. It was observed that tensile and flexural strengths decreased with increasing filler ratios. However, the addition of B4C and Gr fillers enhanced the wear resistance of glass fiber-reinforced composites. It was revealed that in drilling operations, as the feed rate increased, the thrust forces increased, while the cutting speed increased, the thrust forces decreased. It was determined that delamination values in glass fiber reinforced composites decreased as the feed rate increase, while delamination values increased as the cutting speed increased. Generally, the thrust forces, vibration, delamination, and moment values obtained during the drilling of B4C-filled glass fiber composites were found to be higher compared to Gr-filled glass fiber composites.

The influence of B4C content on the pore structure of reaction-synthesized porous Ti3AlC2-TiB2 composite ceramics

Using a mixture of TiH2, Al, B4C, and graphite powders with a molar ratio of 3+2 m/1.2/m/2-m (where m ranges from 0 to 0.25, with increments of 0.05), porous Ti3AlC2-TiB2 composite ceramics were successfully synthesized through activated reaction sintering. The effect of B4C content on the phase composition, volumetric expansion, microstructure, and pore structure parameters (including pore size, porosity, and permeability) was systematically studied. When the molar ratio of B4C was less than 0.1, the volumetric expansion rate, average pore size, and permeability increased with the addition of B4C, reaching maximum values of −5.46 %, 2.23 μm, and 92.4 m3 m−2·10 kPa−1 h−1, respectively. Conversely, when the B4C molar ratio exceeded 0.1, the parameters related to the pore structure of the porous Ti3AlC2-TiB2 composite ceramics decreased, with minimum values of −10.40 %, 1.46 μm, and 68 m3 m−2·10 kPa−1 h−1, respectively. In addition, the pore formation mechanism of the porous Ti3AlC2-TiB2 composite ceramics was systematically explored. The revolution tendency of pores is related to the decomposition of TiH2, Kirkendall partial diffusion, diffusion between B and C, and the transition process of the final phase Ti3AlC2-TiB2. This research work could provide a reference for the preparation of the MAX phase composite porous materials.

Tribology of Mg-B4C nanocomposites fabricated following powder metallurgy route

In this experimental work, magnesium nanocomposite reinforced with various percentage of boron carbide (0.5%, 1.0%, 1.5%, 2.0% by volume) is fabricated using conventional powder metallurgy technique. Characterisation and wear test of the fabricated composite have been performed using scanning electron microscopy, tribology test monitor respectively. It is observed that addition of B4C increases the hardness and wear resistance linearly. Addition of 2% B4C produces the hardness of the nanocomposites as high as 57.93 ± 4.9 Hv. Furthermore, the nanocomposites displayed improved wear resistance and lower friction coefficient compared to the base magnesium. The influence of sliding speed on these properties has been systematically presented. The paper provides an in-depth exploration of wear mechanisms through a meticulous analysis of SEM micrographs of worn surfaces. This work offers valuable insights into the microstructural characteristics and tribological behaviour of Mg-B4C nanocomposites. These findings underscore the potential application of Mg-B4C nanocomposites in the development of lightweight wear-resistant materials. The impact of incorporating minute amounts of nano-sized boron carbide into Mg, on its behaviour under small loads and repeated scratching has been investigated in this study. Moreover, introspection of the wear mechanisms and the effectiveness of the powder metallurgy technique in fabricating composite materials is presented.

Mechanical and ballistic studies of boron carbide filler reinforced glass fiber composites

AbstractOwing to the outstanding properties of boron carbide (B4C) particles, material researchers have shown potential in filler‐reinforced polymer composites. The present work studied the implication of B4C fillers on the mechanical and ballistic properties of glass fiber epoxy reinforced composites. Two different weight percentages of 2 and 4 wt% B4C fillers were used to modify the epoxy resin. The composite samples with glass fabric woven were made through compression molding. The results show that the tensile, flexural, interlaminar, impact strength and hardness of glass fiber composite were improved by addition of 2 wt% of B4C. The high‐velocity ballistic tests were conducted on the unfilled and B4C filler‐reinforced composites using a 9 mm parabellum projectile with an initial striking of 372 ± 15 m/s. The least back face signature (BFS) and highest specific energy absorption (SEA) were observed for 2 wt% B4C filler composite. Adding B4C filler enhanced matrix toughening and interfacial bonding between fiber and matrix. Matrix cracking and fiber breakage result in the least ballistic resistance for unfilled composite. Fracture behavior was studied on tensile, impact, and ballistic‐tested samples using scanning electron microscopy. The fractured surfaces of filler‐reinforced composite demonstrated good interfacial bonding, matrix hardening, and fiber pullouts.Highlights The addition of B4C with epoxy up to 2 wt% improves the mechanical and ballistic properties of the composites. The least back face signature and highest specific energy absorption were observed for 2 wt% B4C filler composite. B4C filler enhanced matrix toughening and interfacial bonding between fiber and matrix. Failure of unfilled glass fiber composites is a combination of matrix cracking, fiber pullout, and interface debonding.

Multi-material structures of Ti6Al4V and Ti6Al4V-B4C through directed energy deposition-based additive manufacturing

The demand for advanced materials has driven innovation in titanium alloy design, particularly in the aerospace, automotive, and biomedical sectors. Additive manufacturing (AM) enables the construction of multi-material structures, offering potential improvements in mechanical properties such as wear resistance and high-temperature capabilities, thus extending the service life of components such as Ti6Al4V. Directed energy deposition (DED)-based metal AM was used to manufacture radial multi-material structures with a Ti6Al4V (Ti64) core and a Ti6Al4V-5 wt.% B4C composite outer layer. X-ray diffraction analysis and microstructural observation suggest that distinct B4C particles are strongly attached to the Ti6Al4V matrix. The addition of B4C increased the average hardness from 313 HV for Ti6Al4V to 538 HV for the composites. The addition of 5 wt.% B4C in Ti6Al4V increased the average compressive yield strength (YS) to 1440 MPa from 972 MPa for the control Ti6Al4V, i.e., >48% increase without any significant change in the elastic modulus. The radial multi-material structures did not exhibit any changes in the compressive modulus compared to Ti6Al4V but displayed an increase in the average compressive YS to 1422 MPa, i.e., >45% higher compared to Ti6Al4V. Microstructural characterization revealed a smooth transition from the pure Ti6Al4V at the core to the Ti64-B4C composite outer layer. No interfacial failure was observed during compressive deformation, indicating a strong metallurgical bonding during multi-material radial composite processing. Our results demonstrated that a significant improvement in mechanical properties can be achieved in one AM build operation through designing innovative multi-material structures using DED-based AM.

Microstructural, mechanical, and biocompatibility properties of Ti–Cu/B4C composites for biomedical applications

This study investigated the effects of B4C on the microstructural, mechanical, and biocompatibility properties of Ti–Cu/B4C composites produced by powder metallurgy. Different amounts of B4C (3, 6, 9, and 12 %) were added to the Ti–Cu matrix. XRD results showed that Ti2Cu, α-Ti, TiB, and B4C phases formed in the microstructure. The addition of B4C and the phases forming in the microstructure resulted in significant increases in the hardness and wear resistance of the composites. SEM images of the wear surfaces showed that the abrasive wear mechanism was dominant. Biodegradability analyses showed that sodium, found in trace amounts in the structure of the alloys, and calcium, released from the structure of B4C into the medium, were the least at the addition of 6 % B4C. Considering the reduced amount of phosphate in the medium, it was found that the mass gain observed in the specimens was due to the deposition of calcium-phosphate precipitates on the surface of the composites. This result suggested that Ti–Cu/B4C alloys were bioactive for bone and may provide osteointegration. Indirect MTT analysis with bone marrow mesenchymal stem cells showed that the specimens were cytotoxic at an acute dose on the first day. However, the cytotoxic effect diminished when they were kept in the PBS medium and replaced every other day for 28 days. Notably, the composite specimen with the addition of 6 % B4C demonstrated maximum cytocompatibility. Consequently, it indicated that adding B4C to the alloy improved osteogenic properties, although it partially increased copper release into the medium.

High compressive strong-ductile tungsten-rhenium alloy via B4C addition

Tungsten-rhenium alloys with high-temperature strength and creep resistance are widely used in the cutting-edge scientific and technological sectors. However, W-5Re alloy with Re content of 5 wt% shows brittleness at room temperature, limiting its aviation temperature measurement. This work provides W-5Re-xB4C (x = 0∼2.0 wt%) tungsten-rhenium alloys with high compressive performance by introducing B4C ceramic phase and regulating the B4C content. The alloys are composed of W(Re) solid solution, W2B phase and a few W2C. When increasing B4C addition, the grain size of the W(Re) matrix decreases from about 200 μm to 17 μm in W-5Re-2B4C and the content of intermetallic compounds increase to be about 12% in W-5Re-0.5B4C and 58% in W-5Re-2B4C. The W-5Re-0.5 wt% B4C alloy exhibits a high yield strength of 1.19 GPa and compressive plasticity with a plastic strain of 42.50%, while the W-5Re-0.75B4C alloy has a high yield strength of 1.52 GPa and good compressive plasticity of 22.52%, obviously higher than the reported W-5Re alloys. Fine-grain strengthening from the refinement of W(Re) and second-phase strengthening from intermetallic compounds simultaneously enhance the alloys, while good deformability of W(Re) metallic phase contributes to the room-temperature plasticity. This study provides necessary data accumulation and theoretical support for the application of tungsten-rhenium alloys.

Construction of three-dimensional network morphology titanium matrix composites via adding nano B4C: As-built and heat-treated scenarios

This study examines the role of nano B4C addition in improving the mechanical properties of Ti–6Al–4V (Ti64) alloys fabricated by laser melting deposition under as-built and heat-treated conditions. However, the enrichment of reinforcing phases generated by in situ production at grain boundaries causes a serious reduction in ductility, limiting the development of high-performance titanium matrix composites. To avoid this deficiency, the fabricated titanium matrix composites (TMCs) were subjected to three different heat treatment programmers, namely, subtransus heat treatment, supertransus heat treatment and triple heat treatment. The effects of B4C addition and heat treatment on microstructure, texture and mechanical properties were systematically investigated. The results show that TiB and TiC, synthesized in situ, promote the precipitation of α-Ti with a non-Burgess orientation relationship, and weakening the texture intensity of α-Ti. The ultimate tensile strength of the in situ synthesized (TiB + TiC) reinforced Ti64 composites is 1168 MPa, which is 35.5 % higher than the ultimate tensile strength of the Ti64 alloys. However, this effect resulted in a decrease in elongation at break to 2.5 %. An excellent combination of strength and fracture strain of 1060 MPa and 9.3 %, respectively, was simultaneously achieved for the heat-treated TMCs. The excellent ductility is mainly attributed to the microstructure consisting of primary equiaxed-α, ultrafine αs lamellar and retained β phase has been obtained after triple heat treatment. This finding offers significant guidance for the additive manufacturing of TMCs microstructures in order to attain the desired mechanical properties.

On the effects of B4C addition on the microstructure, mechanical properties, wear and thermal stability of TiCN- Co -Cr3C2-Si3N4 cermets developed by vacuum hot pressing

This paper reports the development of TiCN - Co - Cr3C2 - Si3N4 cermets modified with the addition of B4C. Cermets of three different compositions with varying B4C in TiCN - Co - Cr3C2 - Si3N4 were fabricated. The TiCN, Co, Cr3C2, Si3N4 and B4C powders in the combinations 80%TiCN-5%Co-5%Cr3C2–5%Si3N4–5%B4C; 75%TiCN-5%Co-5%Cr3C2–5%Si3N4–10%B4C; 70%TiCN-5%Co-5%Cr3C2–5%Si3N4–15%B4C were ground in a ball milling unit for six hours at a speed of 300 rpm at a ball-to-powder ratio of 10:1. The powders were then sintered in a vacuum hot press at a temperature of 1600 °C and a pressure of 50 MPa with soaking time of 90 min. For comparison purpose, 90%TiCN-5%Co-5%Cr3C2 cermet was prepared. The microstructure of the sintered cermets revealed the core-rim structure. The Vickers hardness test was done with a load of 10 Kg and for duration of 10 s. Fracture toughness was measured using the crack length data obtained from the hardness test using scanning electron microscopy. The cermet with a composition 75% TiCN-5%Co-5% Cr3C2–5% Si3N4–10% B4C produced higher hardness of 26.53 ± 0.56 GPa and fracture toughness of 10.29 ± 0.18 MPam and 70% TiCN-5%Co-5% Cr3C2–5% Si3N4–15% B4C showed high fracture toughness value of 11.23 ± 0.09 MPam with hardness value of 21.05 ± 0.10 GPa. The cermet composition 75% TiCN-5%Co-5% Cr3C2–5% Si3N4–10% B4C retained the hardness of 16.85 GPa even after annealing at 600 °C. The sintered cermets tend to form TiO2 which determines the hardness of the annealed cermets at a range of 600 °C – 1000 °C. The presence of these oxides tends to decrease the hardness. The wear test was performed taking the cermet as the pin material. The abrasive and adhesive wear mechanisms were dominant in the cermets. The harder precipitates formed tend to increase wear resistance by reducing the wear rate. The harder precipitates (TiN and TiB2) formed mainly due to the addition of Si3N4 and B4C, this addition promotes adhesive wear by a tribolayer formation.

Microstructural evolution and mechanical properties of titanium matrix composites with second-phase dendritic TiC improved through B4C additions

Titanium matrix composites with high TiC content have multiple excellent properties. However, their dendritic TiC morphology poses challenges to their room-temperature plasticity. In this study, (TiC + TiB)-reinforced titanium matrix composites were developed by incorporating B4C into dendritic TiC composites. The impact of B4C additions on the microstructure evolution and mechanical properties of dendritic TiC in the composites was systematically investigated. The results revealed that the in-situ synthesis of TiC and TiB significantly refines the matrix grains of the composites with the addition of B4C. Notably, TiB serves as a nucleation substrate for dendritic TiC, forming an intergrowth microstructure of TiC and TiB during solidification–precipitation. This effectively reduces the number of dendritic TiC. The interfacial orientation relationships between TiC and TiB were studied through high-resolution transmission electron microscopy, revealing [110]TiC//[311]TiB and (111)TiC//(210)TiB, with a two-dimensional lattice mismatch of 6.43% between (111)TiC and (210)TiB. At room temperature, the ultimate tensile strength and fracture strain of the composite with 1 wt% B4C were 1059.52 MPa and 5.58%, respectively. Compared with the original composite, the tensile strength increased by 39.4%, and the corresponding elongation was remarkably increased. This enhancement is attributed to the synergistic strengthening effect and fine grain strengthening effect of the intergrowth structure of TiC and TiB in the composite. The microstructure refinement mechanism and strengthening mechanism are discussed in detail, providing new ideas and methods for the design and preparation of composites.

Thermal shock effects on the microstructure and mechanical properties of iron-based composites reinforced by in-situ Fe2B/FeB ceramic phases

Recently, high-temperature composites reinforced with in-situ phases have been developed as a new class of composites for harsh environments. The behaviour of these composites under sudden heating and cooling conditions is greatly influenced by the type and fraction of components. The aim of this study is to investigate the microstructural properties and mechanical response of iron based composites after thermal shock cycling. The fabrication process involved in-situ powder metallurgy (IPM) sintering of Fe–B4C starting powders. The samples were subjected to thermal shock with a constant temperature differences (ΔT: 600 °C) and varied cycles (N: 1–50). Comparison of microstructural changes and mechanical behaviour before and after thermal shock has been carried out. The boron atoms released from the initial B4C generated diffusion zones in the matrix dominated by iron boride phases (Fe2B/FeB). An effective matrix-reinforcement interface has been created by in-situ powder metallurgy, where boride phases are almost homogeneously distributed in the iron matrix. While the hardness of the composites was significantly developed by the Fe2B/FeB phases, the addition of B4C resulted in a reduction in the coefficient of thermal expansion (CTE). The in-situ phases contributed in the minimisation of the coefficient mismatch by balancing the thermal expansion coefficients between iron and the initial B4C. Under the influence of thermal shock, microcracks and then macrocracks formed on the sample surfaces, increasing in width and depth with thermal cycles. This resulted in accelerated fracture damage under post-thermal loading. Both the impact and flexural strengths of the samples were significantly reduced as the number of thermal cycles increased. Although the 20% B4C reinforced composite provided maximum hardness, it showed poor resistance to thermal loading. The best results for mechanical loads were achieved by the 5% B4C reinforced composite, which showed no cracks even after 50 thermal cycling.

“Evaluation of microstructure and mechanical properties of Al6005 MMCs reinforced with B4C via stir casting route and optimisation through ANOVA DOE technique”

ABSTRACT MMCs are used in variety of applications due to their distinctive characteristics, including superior stiffness, wear resistance and service temperatures, brake rotor, cylinder liners, automobile drive shaft, and connecting rod. In the present studies, Al6005-B4C composites were developed using the gravity die-casting technique to investigate mechanical properties (hardness and tensile strength). Later, microstructural characterisation is conducted using an optical microscope. Also, fracture surface analysis was carried out using SEM. The optical micrographs revealed that Al6005 alloy has a fine-grained, uniform microstructure and Al6005-B4C MMCs. Also, SEM fractographs of Al6005 displayed ductile fracture due to more dimples, and Al6005-B4C MMCs exhibited brittle fracture. From the hardness and tensile test results, it is noticed that the addition of B4C enhances the mechanical properties of Al6005-B4C MMCs. Overall, it is observed that the hardness and strength value steadily increase up to 4% B4C as the reinforcement percentage grows and then somewhat decrease when the B4C addition is improved to 6%. The accumulation of particles in the matrix may be the cause. The regression analysis results confirm that the coefficient of determination was achieved with an 86% of confidence interval, and the P-values is less than 0.05 for all the combination considered.

Pressureless densification and properties of high-entropy boride ceramics with B4C additions

High entropy boride ceramics have great potential as structural materials serving in extreme environments. However, their applications are limited by the difficulty of sintering. In the present study, dense (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)B2 ceramics with B4C additions were prepared through pressureless sintering at as low as 1900 °C. Calculations based on the CALPHAD approach predict that (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)B2 starts to melt at about 3315 °C whilst B4C additions reduce the temperature and broaden the temperature region where solid and liquid coexist. Results showed that the introduction of B4C could trigger the densification of (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)B2 at a lower temperature and promote their densification significantly. The relative density of samples with 5 wt% of B4C additions sintered at 1900 and 2000 °C was 97.7 % and 99.7 %, respectively. While the sintering temperature was further increased to 2100 °C, the liquid phase was reactively formed, leading to the rapid grain coarsening in samples with B4C additions. Strengthened by well-dispersed B4C grains, the sample with 5 wt% B4C sintered at 2000 °C exhibited excellent mechanical properties with the Vickers hardness, flexural strength, and fracture toughness of 21.07 ± 2.09 GPa, 547 ± 45 MPa, and 5.24 ± 0.14 MPa m1/2, which are comparable or even higher than counterparts sintered under pressure.

Spark plasma sintered TiB2-SiC UHTC derived from B4C and stoichiometric intermetallic phases from Ti-Si system

Previously conducted studies determined that the reactive sintering of B4C and stoichiometric additions of TiSi2 or Ti5Si3 intermetallics created a dense TiB2-SiC double-phase system that could be classified as ultra-high temperature ceramics (UHTC). In this work, a spark plasma sintering (SPS) technique was used to improve the sintering process and thus further reduce the obtaining temperature and improve the final microstructure and mechanical properties of the proposed, double-phase TiB2-SiC UHTC systems. To evaluate the effects of the experiment, a comprehensive study of phase composition, microstructure and mechanical properties was added. As a result, minimal sintering temperatures were further reduced from 1420 - 1650 ºC to a range of 1200–1400 ºC. Among the prepared composites those sintered at 1400 ºC achieved the best properties. The prepared composites maintained high hardness (up to 24.85 GPa), high tensile strength (up to 309 GPa), relatively high fracture toughness (up to 4.80 MPa∙m1/2) and relatively low density, all of which characterized TiB2-SiC UHTC systems.

Improving the mechanical properties and oxidation resistance of Nb-16Si-20Ti alloys with B4C addition

Nb-Si-based alloys, as one of the candidate materials which may replace nickel-based alloys for the next generation aero-engines, its low fracture toughness (KQ) and poor oxidation resistance severely limited their application and development. Research has shown that Nb-Si-based alloys with a refined microstructure usually have good fracture toughness, whereas B and C elements are good microstructure refinement elements. So, the effects of B4C on the microstructure evolution and properties of Nb-16Si-20Ti alloys were studied. The results showed that the microstructure of Nb-16Si-20Ti was composed of Nb-based solid solution (Nbss) and Nb3Si phases. With the addition of B4C, the coarse Nb3Si decomposed and transformed into (α, γ)-Nb5Si3 + Nbss eutectic structure, refining the microstructure of the alloys. The room temperature fracture toughness and compressive strength of Nb-16Si-20Ti alloy were improved by adding B4C, among which the fracture toughness of 0.50B4C alloy was up to 11.5 MPa·m1/2, which increased by 98.3% compared with that of the 0B4C alloy. The improvement of the fracture toughness was mainly due to the increment of the ductile Nbss content in the alloy and the refinement of the microstructure. In addition, the addition of an appropriate amount of B4C (≤0.5 at.%) also improved the oxidation resistance of Nb-Si-based alloys.