TiB2 Phases Research Articles

In situ TiBX/TiXNiY/TiC reinforced Ni60 composites by laser cladding and its effect on the tribological properties

Ni-based composite coatings reinforced by TiBX/TiXNiY/TiC with different Ti6Al4V contents were precipitated on a 35CrMoV substrate via laser cladding. The phase composition, elemental distribution, and precipitated phases of the coatings were characterised using X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electron microscopy, and transmission electron microscopy. The mechanical and tribological properties of the cladding layer were also characterised. The results showed that the coating contained TiB2, TiC, TiB, Ni3Ti, and NiTi2 phases with uniform elemental distribution and grain refinement. A schematic of the growth model and precipitation sequence of the reinforced phases was generated. The microstructure, elemental segregation, hardness, and friction behaviour of the cladding layer were significantly influenced by the addition of Ti6Al4V. The optimal microstructure and best mechanical properties were obtained by the addition of 4 wt% Ti6Al4V, with that coating possessing a hardness, average friction coefficient, and wear volume of 770.8 HV1, 0.180 and 6132 um3, respectively.

Microstructure evolution and mechanical response of a boron-modified Ti–6Al–4V alloy during high-pressure torsion processing

Research was conducted on the microstructural evolution and ensuing mechanical response from high-pressure torsion (HPT) processing of Ti–6Al–4V alloy in the as-cast and β-forged conditions with and without 0.1 wt% boron addition. The boron addition produces refinement of the prior β grains and the (α+β) colonies and introduces an additional TiB phase but this affects the deformation response and the microstructural evolution only at low strains of 0.5–5 rotations. In the initial condition the orientation of the (α+β) colonies significantly affects the deformation response and leads to differences in substructure formation in both the as-cast and β-forged conditions. This orientation dependence counts on the initial microstructural differences between the unmodified and the boron modified alloys. At higher strains, there is a similar deformation response and microstructure evolution for all the alloys. The hardness variation with equivalent strain is similar for the unmodified and boron modified alloys in as-cast and β-forged conditions and represents various deformation regimes in HPT-processing. Strength modelling confirms a simultaneous contribution from microstructural refinement and increased dislocation density towards the hardness increment during HPT processing. Overall, the as-cast and β-forged Ti–6Al–4V-0.1B alloys possess identical deformation response to the β-forged unmodified Ti–6Al–4V alloy in the initial and intermediate stages. At high levels of straining, all alloys respond in an equivalent manner, thus ruling out any possible effects from additional TiB phase or microstructural refinement for the boron-modified alloys.

Effect of ceramic-binder interface on the mechanical properties of TiB2-HEA composites

A non-equiatomic CoCrFeNiMo high-entropy alloy (HEA) was used as a binder for the TiB2-HEA composites. The TiB2–6 vol% HEA and TiB2-10 vol% HEA composites were successfully fabricated by mechanical alloying and spark plasma sintering. Phase analysis revealed the presence of FCC and TiB2 phases in the composites. A detailed microstructural study using scanning electron microscopy and transmission electron microscopy helped with the understanding of the impact of carbide/binder interface on fracture toughness and strength of the TiB2-HEA composites. TEM revealed a few nanometer-thick intermediate layer between the TiB2 and HEA phases that facilitates the enhanced wettability between ceramic and binder phase. The fracture mode was affected by the HEA binder concentration, i.e., the dominant mode of fracture changed from intergranular to transgranular as binder content increased from 6 vol% to 10 vol%. The relative density, Vickers hardness and fracture toughness of TiB2-10 vol% HEA composite reached up to 98.50 ± 0.30%, 22.00 ± 0.62 GPa and 9.23 ± 0.45 MPa m1/2, respectively. The high fracture toughness of the TiB2-10 vol% HEA composite was the result of the synergism of high densification, excellent wettability, crack deflection, crack bridging, and transgranular fracture of the TiB2 particles.

Microstructural Characteristics of Ti‐Based Composites with Various Ceramic Reinforcements Manufactured via Hydrogen‐Assisted Blended Elemental Powder Metallurgy

The manufacturing of in situ reinforced titanium matrix composites by the sintering of titanium hydride and ceramic powder blends is an attractive and cost‐efficient process. Herein, a novel two‐stage (double‐compaction/double‐sintering) hydrogen‐assisted powder approach is suggested to produce uniform highly dense Ti‐based composites reinforced with TiB, TiC, and dual TiC + TiB phase particles. In this approach, the hydrogenation and milling of presintered products enable the initial porous materials to transform into hydrogenated prealloyed (PA) powders of controlled sizes, and a second press‐and‐sinter process further converts the PA powders into nearly dense composite microstructures with evenly distributed fine reinforcements. The adverse effect of the raw reinforcing powder size on microstructure uniformity, porosity, and mechanical characteristics of the presintered in situ composites becomes negligible in final sintering stage. The reduction of the porosity and enhancement of the hardness indicate that the hydrogen‐assisted double‐compaction and double‐sintering blended elemental powder metallurgy (BEPM) + PA approach enables the low‐cost fabrication of Ti‐based composites with suitable mechanical characteristics.

Preparation of high-hardness titanium oxycarbonitride ceramic and its composite with TiB2

Dense titanium oxycarbonitride (TCNO) ceramic and its composites with in-situ grown and direct-added TiB2 particles were prepared by powder sintering. The TCNO ceramic is a single-phase solid solution and its composites mainly contain TCNO phase and TiB2 phase. The in-situ grown TiB2 grains have an average size about 2.3 μm and the plate-like morphology, and the direct-added TiB2 form spherical grains with the average grain size about 2.0 μm. Meanwhile, the introduction of the secondary phase of TiB2 reduces the TCNO grain size. Compared to the hardness of pure TCNO ceramic about 27.7 GPa, the hardness of its composites is increased to above 30 GPa. The outstanding hardness of TCNO ceramic and its composites is attribute to the synergistic effect of solid-solution reinforcement and the introduction of secondary phase of TiB2.

Tribological behaviour of TiB2 ceramic based composite coating deposited on stainless steel AISI 304 by gas tungsten arc (GTA) cladding process

In this study, Titanium (Ti)-Titanium diboride (TiB2) metal matrix composite (MMC) cladding layers were fabricated on an AISI 304 stainless steel substrate by the gas tungsten arc (GTA) cladding process. The composite cladding layer was produced using different powder mixtures: 85 wt% TiB2−15 wt% Ti, 75 wt% TiB2−25 wt% Ti, and 65 wt% TiB2 −35 wt% Ti. During cladding, the GTA process currents were used in the range of 70 A to 90 A with 10 A interval differences and the scan speed in the range of 1.1 mm sec−1 to 1.9 mm s−1 with 0.4 mm s−1 interval differences. All samples were investigated for mechanical properties, microstructure, and phase analysis by Vickers microhardness, scanning electron microscopy (SEM), Energy dispersive x-ray spectroscopy (EDX), and x-ray diffraction (XRD) respectively. The x-ray diffraction (XRD) findings indicate that the composite coatings consist of TiB2, TiB, Ti, Fe3C, B4C, and NiTi phases. The presence of elements B, C, Ti, Cr, Mn, Fe, and Ni in the coating was confirmed by x-ray energy dispersive spectroscopy (EDX). The maximum microhardness value of the composite coating was enhanced in the range of 1639 HV0.1 to 3781 HV0.1, whereas the microhardness of the AISI 304 stainless steel substrate was 194 HV0.1. The average wear rate of the coated samples was determined in the range of 11.09 × 10−9 g N−1-m−1 to 27.63 × 10−9 g N−1m−1, whereas the average wear rate of the AISI 304 steel substrate was 88.414 × 10−9 g N−1m−1. It can be concluded that the maximum micro-hardness of the composite coating increased by 9-19 times than that of the nominal substrate (AISI 304 stainless steel). Also, the wear resistance of the composite coating enhanced by 8 times as compared to AISI 304 steel substrate. It is demonstrated in this study that the processing current, TiB2 content, and scanning speed have significant effect on the microstructure, mechanical, and tribological features of the cladding layers under consideration.

Effect of CeO2 on the TiB2 + TiC evolution and water droplet erosion resistance of laser-clad Ni60A coatings

In this study, CeO2-doped Ni60A coating was fabricated on the surface of Ti6Al4V alloys. During the fabrication, heterogeneous nucleation occurred between TiB2 and TiC phases within Ni60A coatings, and the TiB2 + TiC eutectic structure was thereby generated. Ce2O3 phases were formed in-situ by the decomposition of CeO2 powder in the molten pool. On the grain boundary of the CeO2-doped Ni60A coating, Ce2O3 particles were distributed, which inhibited the growth of hard phases TiC and TiB2. Compared with the coating without adding CeO2 powder, the CeO2-doped Ni60A coating had significantly lower crack sensitivity, and the TiB2 phase in the CeO2/Ni60A coating had a far smaller grain size due to the grain refinement effect. In addition, the TiC + TiB2 eutectic structure acted as the skeleton in the coating, enabling the coating to effectively resist the shear effect caused by high-speed water particles. After coating Ni60A and CeO2/Ni60A on the Ti6Al4V alloy, the water droplet erosion depth of the alloy was reduced by 38.7% and 53.2%, respectively. Therefore, adding CeO2 powder into Ni60A coatings has great application value in improving the water droplet erosion resistance of steam turbine blades.

Design and characterization of in-situ TiB reinforced TiB/Ti50Zr25Al15Cu10 non-equiatomic medium-entropy alloy composite coating on magnesium alloy by laser cladding

The improvement of corrosion resistance and wear resistance levels is of great significance because of the far-ranging impacts of them on the further application of magnesium alloys. In this work, a novel TiB/Ti50Zr25Al15Cu10 medium-entropy alloy composite coating (MEACC) was successfully prepared on the surface of magnesium alloy by laser cladding. The effect of LaB6 content on microstructure, micro-hardness, wear resistance and corrosion resistance of Ti50Zr25Al15Cu10 coatings was studied in detail. The results show that TiB/Ti50Zr25Al15Cu10 MEACCs are mainly composed of α-Ti, BCC and TiB phases. With LaB6 content increased, the microstructure of the coating is refined and homogenized. And when the addition amount is excessive, Cu2La clusters appear. The lattice distortion caused by La3+ with large ion radius leading to the formation of hard BCC solid solution, as well as the dispersion strengthening of TiB in-situ, the coating presents high micro-hardness and excellent wear resistance. Especially, the average micro-hardness values of Ti50Zr25Al15Cu10 coating with 4 wt% LaB6 is ∼679.4 HV0.3, which is about 11 times than that of the substrate (∼61.6 HV0.3). Besides, TiB/Ti50Zr25Al15Cu10 MEACC displays excellent corrosion resistance. The minimum corrosion current density is 8.52 × 10−7 A·cm−2, and the oxidation phenomenon emerged in the coating. The oxide film is mainly composed of the oxidation state of Ti, Zr, Al, Cu and the sub-oxide state of Cu.

In Situ Investigation of Deformation Mechanisms Induced by Boron Nitride Nanotubes and Nanointerphases in Ti–6Al–4V Alloy

There is a need to augment the mechanical strength of titanium alloys to take advantage of their low mass density for structural applications. Herein, the reinforcement potential of boron nitride nanotube (BNNT), a high‐aspect‐ratio nanomaterial with exceptional strength and thermal stability, to engineer nanocomposites based on Ti–6Al–4 V alloy, is interrogated. The stress‐transfer behavior at the matrix/filler interface is programmed by tweaking the extent of chemical reactions during sintering. A twofold improvement in indentation resistance after integrating BNNTs in the alloy due to the crack bridging mechanism is reported. There is a further 50% enhancement in hardness and stiffness as the sintering temperature is raised from 750 to 950 °C. This improvement is attributed to the escalated formation of TiN and TiB phases due to matrix–nanotube interfacial reactions at elevated temperatures. A novel indentation‐based in situ trench testing technique is employed to study the subsurface deformation mechanisms activated in the bulk of the composite specimen. The ceramic interphases promote the indentation resistance by acting as crack deflectors in the microstructure, which promotes the dissipation of mechanical work. These insights can be applied to designing Ti‐BNNT microstructures with desired mechanical properties and deformation characteristics.

Assessment of mechanical properties of LM13 aluminum alloy hybrid metal matrix composites

Aluminium LM13 alloy based hybrid particulate composites have been processed by adding boron carbide (B4C) and titanium diboride (TiB2) particles. The wt% of titanium diboride (TiB2) is varied as 0, 3, 6, 9, 12, 15 and a constant 3 wt% of boron carbide is used to prepare the composites. Stir cast route is used to fabricate the composites. The microstructures of castings are examined using computer aided image analyzer. Vicker hardness, yield strength, ultimate tensile strength and energy absorbed by the composites are examined and reported. The results show that uniform dispersion of TiB2 and B4C reinforcement phases in Al LM13 alloy. Micro hardness of composites enhanced upto 36.6% when compared to Al alloy reinforced with 3 wt% of B4C particles. Ultimate tensile strength of Al alloy is improved from 151 MPa to 192 MPa by reinforcing 15 wt% of titanium diboride particles. LM13 aluminium alloy hybrid particulate composites offers superior vicker hardness, yield strength, utlimate tensile strength and impact strength over LM13 aluminium alloy based single particle reinforced composites.

Microstructure and mechanical property of in-situ synthesized SiC–TiB2 porous ceramic as a function of TiB2 content

A convenient and promising one-step manufacturing processes was successfully developed to fabricate SiC–TiB2 porous ceramics. TiO2, B4C and sucrose were used as raw materials for in-situ generation of TiB2 phase, which promoted skeleton grain bonding and achieved highly interconnected pores simultaneously. The effect of different TiB2 volume fractions on porous structures, pore parameters, and mechanical properties was studied. SiC–TiB2 porous ceramics were obtained with porosities ranging from 36.2% to 41.9%, pore sizes ranging from 2 μm to 10 μm, and high compressive strength up to 169.5 MPa. Apart from the total porosity, TiB2 content, as well as pore/skeleton characteristics, were demonstrated as important factors affecting the mechanical properties. Hence, based on the strength-porosity relationship, an extended equation was proposed for modelling and optimizing the mechanical properties of biphasic porous ceramics.

HRTEM and XPS characterizations for probable formation of TiBxNy solid solution during sintering process of TiB2–20SiC–5Si3N4 composite

The microstructural characterization of spark plasma sintered (SPSed) TiB2–20SiC–5Si3N4 composite was investigated precisely by high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). The in-situ phases generated during SPS process were studied using HSC chemistry software; the result shows the development of plausible reaction between Si3N4 and B2O3, forming h-BN. In addition, the formation of in-situ TiN phase and/or TiBxNy solid solution was confirmed by XPS analysis, attributed to the reaction between TiO2 and Si3N4. The intense interfaces were formed due to the coherency between hexagonal structures of TiB2, SiC, and BN phases as detected by HRTEM. Furthermore, weak interfaces were generated because of the formation of amorphous phases in the junctions. The presence of structural defects and distortions was demonstrated in both TiB2 and h-BN by inverse fast Fourier transform patterns, which can be considered as the main channels for the diffusion and transportation of boron atoms into the Si3N4 matrix for the formation of the in-situ h-BN phase.

Titanium boride and titanium silicide phase formation by high power diode laser alloying of B4C and SiC particles with Ti: Microstructure, hardness and wear studies

In this work a novel multiphase titanium metal matrix composite (TMMC) coating was developed by high power diode laser assisted alloying of Cp-Ti with the preplaced Boropak powder consisting of B4C and SiC ceramic particles. The XRD, optical microscopy, scanning electron microscopy, EDAX, microhardness and wear testing techniques were employed to investigate structural phase, hardness and wear properties of the alloyed coating. Under the influence of multipass laser alloying, the B4C and SiC ceramic particles decompose to yield boron, silicon and carbon species that react with molten titanium to form TiB2, TiB, TiC and Ti5Si3 phases in the laser alloyed coating. In addition, the un-melted B4C and SiC ceramic particles are dispersed in the titanium matrix. Microstructure of the alloyed coating consists of dendrites and coralline-like structure. The tips of the coralline-like structure are in the range of 150–500 nm. The ceramic multiphase TiB2, TiB, TiC and Ti5Si3 formation resulted in average microhardness around 800–2200 HV0.2 at different regions of the TMMC coating cross section. To correlate the phase formation and microstructural features, surface temperature evolved at the interaction area during laser surface alloying was estimated by a simple equation. Activation energy for the laser melted track was calculated using the Arhennius equation. The linear reciprocating wear test performed on laser alloyed coating against WC ball showed wear rate value of 1.623 х 10−4 mm3/N.m which is 6 times lower compared to the untreated titanium.

Experimental and first-principles study on TiB/TiC interface in hybrid (TiB+TiC)/Ti6Al4V composite

To understand the synergistic strengthening mechanism of hybrid TiB + TiC reinforcements in Ti matrix composites, the corresponding TiB/TiC interfacial characters and load-bearing capacity were revealed in this work through a coupled method of high-resolution transmission electron microscopy (HRTEM), ab-initio calculations, and Vickers indentation test. Results show the interfacial orientation relationship (OR) between TiB and TiC phases is [010]TiB//[11 2‾]TiC, (2 2‾ 0)TiC//(102)TiB, which exhibits an interface formation energy of 3.32 J/m2 estimated via first-principles calculations. The TiB/TiC interface shows a high adhesion strength of 5.78 J/m2 owing to the formation of strong B–C covalent bond, which is also slightly higher than the strength (5.52 J/m2) obtained within TiB. Moreover, the strong TiB/TiC interface contributes to the superior load-bearing capacity of the intergrowth ceramic structure with relatively higher hardness (∼2100 HV0.2) than that of individual TiB and TiC phases (around 2020–2030 HV0.2). Consequently, the hybrid TiB + TiC reinforcements exhibit a synergistic strengthening effect in Ti matrix composites due to the intergrowth microstructure characteristic with superior load-bearing capacity.

Optimization of core–shell structure distribution in sintered Nd-Fe-B magnets by titanium addition

In view of the uneven distribution of the core–shell structure of sintered Nd-Fe-B magnets after grain boundary diffusion, this study proposes to use high-melting-point and reactive element titanium (Ti) as an additive to increase the diffusion channels and to enhance the diffusion of heavy rare earth elements along the grain boundary phase. By adding Ti element, the diffusion depth and hence the intrinsic coercivity of magnets are increased significantly. The addition of Ti increases the coercivity at two stages: initially from 16.07 to 16.29 kOe by addition effect, and then from 16.29 to 25.16 kOe by facilitating the diffusion of Tb element. The formation of TiB2 phase improves the periodic arrangement of the crystal structure in the surroundings of the grain boundary phase and enhances its activity. The improved grain boundary diffusion and better core-shell structure distribution provide a theoretical guidance for solving the problem of diffusion depth in bulk magnets.

Impurity-impurity interaction during the growth of UMG-Si-based mc-Si

This article investigates the relationship between the chemical composition and electrophysical properties of p- and n-type multicrystalline silicon ingots based on metallurgical silicon with a purity of 99.99 at.%. In particular, the role of impurity-impurity interactions in the production of multisilicon by the Bridgman vertical method is evaluated in order to identify approaches to controlling this process effectively. The phase equilibrium calculations in the “silicon–all impurities” and “silicon-impurity-oxygen” systems were carried out based on the Gibbs energy minimization in the Selector software package. The study investigates the rank correlations of the concentrations of various impurities with each other, as well as with the specified electrical resistivity (SER) and the lifetime of nonequilibrium charge carriers (NCC) in the direction of crystal growth. Pair correlations of the element distribution profiles were considered based on the role of the main factor represented by the ratio of individual impurity solubilities in solid or liquid silicon (k0), as well as from the standpoint of direct interaction between two elements. It was found that the k0 value for two individual impurities in silicon does not automatically lead to the pair correlation of their distribution profiles in the ingot. A significant effect on the distribution profiles of impurities in multisilicon with k0→0 has the factor of binding some part of the impurity into such a form that this impurity can be incorporated easily into a growing crystal. Binding may be induced by the interaction of the impurity in the melt with the oxygen background, its segregation at the grain boundaries, and its capture by the crystallization front in the composition of the liquid inclusion. Significant correlations of impurity distribution profiles in the ingot were demonstrated by the pairs whose elements interact without the formation of chemical compounds in the 25–1413 °C temperature range. The conducted phase equilibrium calculations for the “silicon–all impurities” system revealed the possibility of forming the VB2, TiB2, ZrB2, and MgTiO4 solid phases in the melt.

Research on dielectric and microwave absorbing properties of TiO2/TiB2/Thermoplastic polyurethanes (TPU) composite materials

TiO2/TiB2 materials are prepared by the carbothermal method and high-temperature calcination. Further, the phase composition, microstructure, dielectric and electromagnetic (EM) wave absorption characteristics are investigated. The results display that the product is composed of TiO2, TiB2 and impurity phases. The complex permittivity increases at elevated TiO2/TiB2 loading and slowly decreases with rising frequency in 2-18 GHz. When the TiO2/TiB2 content is 45 wt%, the minimum reflection loss (RLmin ) reaches -43.12 dB at 11.68 GHz with a thickness of 1.9 mm. The effective absorption band (EAB, RL<-10 dB) can reach 3.68 GHz at 2.3 mm as the TiO2/TiB2 content is 30 wt%. The enhanced EM wave absorption owes to the strong polarization loss and high conductivity loss. It goes without saying that TiO2/TiB2 materials can acquire important breakthroughs in the development of novel EM wave absorbers with outstanding absorption loss, wider EAB and smaller thicknesses.

Residual Stress Induced by Addition of Nanosized TiC in Titanium Matrix Composite.

A hot pressing process was employed to produce titanium-based composites. Nanosized TiC particles were incorporated in order to improve mechanical properties of the base material. The amount of nanosized additions in the composites was 0.5, 1.0, and 2.0 wt %, respectively. Moreover, a TiB phase was produced by in situ method during sintering process. The microstructure of the Ti–TiB–TiC composites was characterized by scanning electron microscopy (SEM), electron probe microanalysis (EPMA), electron backscatter diffraction (EBSD), and X-ray diffraction (XRD) techniques. Due to the hot pressing process the morphology of primary TiC particles was changed. Observed changes in the size and shape of the reinforcing phase suggest the transformation of primary carbides into secondary carbides. Moreover, an in situ formation of TiB phase was observed in the material. Additionally, residual stress measurements were performed and revealed a mostly compressive nature with the fine contribution of shear. With an increase in TiC content, linear stress decreased, which was also related with the presence of the TiB phase.

Duplex Nucleation and Its Effect on the Grain Size and Properties of Near Eutectic Al-Si Alloys

Duplex nucleation and its effect on the grain size and properties of near eutectic Al-Si alloys were investigated in this work. It is found that the grain size of Al-13Si-1Cu alloy can be greatly refined by addition of Al-2Ti-0.5B-0.5C and Al-P master alloys, and TiB2/AlP duplex nucleation was observed at the nuclei of primary silicon in the process of studying the refinement mechanism. TiB2 phase coated by Al co-existed with AlP in the nuclei of primary Si. The existence of Al phase should not only guarantee the promotion of TiB2 particles on the nucleation of AlP particles, but also made TiB2 particle stable in the core of primary silicon through the interaction with the Si phase. Duplex nucleation can not only affect the grain size of Al-Si alloy, but also effect of the distribution of strengthening phases in Al-Si alloy and improve the properties. Compared with single Al-P master alloy treatment, the tensile strength of Al-12Si-4Cu-2Ni-1Mg alloy after duplex nucleation treatment are improved obviously. The fatigue performance of Al-12Si-4Cu-2Ni-1Mg alloy is also improved significantly by the duplex nucleation.

Long-whisker type TiB phase introduced by micron-sized precursors and its prominent strengthening effect in titanium matrix composites

We developed a new strategy to obtain long whisker (LW) TiB phase (aspect ratio as high as ∼150) using micron-sized AlB2 in a series of TiB/Ti(Al) composites. While three types of TiB phases were present in the composites, microhardness and compression results show that LW-type TiB enhances yield strength dramatically.