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Metal matrix composites tiles based on Ti–6Al–4V (Ti64) alloy, reinforced with 10, 20, and 40 (vol%) of either TiC or TiB particles were made using press-and-sinter blended elemental powder metallurgy (BEPM) and then bonded together into 3-layer laminated plates using hot isostatic pressing (HIP). The laminates were ballistically tested and demonstrated superior performance. The microstructure and properties of the laminates were analyzed to determine the effect of the BEPM and HIP processing on the ballistic properties of the layered plates. The effect of porosity in sintered composites on further diffusion bonding of the plates during HIP is analyzed to understand the bonding features at the interfaces between different adjacent layers in the laminate. Exceptional ballistic performance of fabricated structures was explained by a significant reduction in the residual porosity of the BEPM products by their additional processing using HIP, which provides an unprecedented increase in the hardness of the layered composites. It is argued that the combination of the used two technologies, BEPM and HIP is principally complimentary for the materials in question with the abilities to solve the essential problems of each used individually.

Metal matrix composites tiles based on Ti-6Al-4V (Ti64) alloy, reinforced with 10, 20, and 40 (vol%) of either TiC or TiB particles were made using press-and-sinter blended elemental powder metallurgy (BEPM) and then bonded together into 3-layer laminated plates using hot isostatic pressing (HIP). The laminates were ballistically tested and demonstrated superior performance. The microstructure and properties of the laminates were analyzed to determine the effect of the BEPM and HIP processing on the ballistic properties of the layered plates. The effect of porosity in sintered composites on further diffusion bonding of the plates during HIP is analyzed to understand the bonding features at the interfaces between different adjacent layers in the laminate. Exceptional ballistic performance of fabricated structures was explained by a significant reduction in the residual porosity of the BEPM products by their additional processing using HIP, which provides an unprecedented increase in the hardness of the layered composites. It is argued that the combination of the used two technologies, BEPM and HIP is principally complimentary for the materials in question with the abilities to solve the essential problems of each used individually. [ABSTRACT FROM AUTHOR]

Single composites are replaced by hybrid composites because of their highly efficient properties and easy processing ability. In this research work, the stir casting process has been used for the fabrication of an Aluminium 6351 metal matrix composite. The TiB2, Graphene and Rice Husk Ash (RHA) have been used as reinforcements. The various mechanical (hardness, impact, flexural, tensile) and surface (SEM, EDS, XRD) characterization have been carried out. The different samples with varying compositions of Graphene (0.0, 0.5, 1.0 and 1.5 wt.-%), the constant composition of Titanium boride (10 wt.-%) and Rice Husk Ash (2.0 wt.-%) have been fabricated. The maximum values of hardness and energy absorbed were 78.8 HV0.3 and 6 Joule respectively and minimum surface roughness of 0.308 µm have been obtained by doping 1.5 wt.-% Graphene in AA6351. Whereas, the maximum value of flexural and tensile strength was 418.73 and 154.81 MPa for AA6351 having 0.5 wt.-% of Graphene as reinforcement. Moreover, the presence of TiB2, Graphene, and RHA showed their uniform distribution in fabricated composites using surface characterization (such as SEM, EDS and XRD). [ABSTRACT FROM AUTHOR]

The mechanical behavior of titanium alloys has been mostly studied in quasi-static conditions when the strain rate does not exceed 10 s-1, while the studies performed in dynamic settings specifically for Ti-based composites are limited. Such data are critical to prevent the strength margin approach, which is used to assure the part performance under dynamic conditions in the absence of relevant data. The purpose of this study was to obtain data on the mechanical behavior of Ti-based composites under dynamic condition. The Metal Matrix Composites (MMC) on the base of the alloy Ti-6Al-4V (wt.%) were made using Blended Elemental Powder Metallurgy with different amounts of reinforcing particles: 5, 10, and 20% of TiC or 5, 10% (vol.) of TiB. Composites were studied at high strain rate compression ~1-3 × 103·s-1 using the split Hopkinson pressure bar. Mechanical behavior was analyzed considering strain rate, phase composition, microstructure, and strain energy (SE). It is shown that for the strain rates up to 1920 s-1, the strength and SE of MMC with 5% TiC are substantially higher compared to particles free alloy. The particles TiC localize the plastic deformation at the micro level, and fracturing occurs mainly by crushing particles and their aggregates. TiB MMCs have a finer grain structure and different mechanical behavior. MMC with 5 and 10% TiB do not break down at strain rates up to almost 3000 s-1; and 10% MMC surpasses other materials in the SE at strain rates exceeding 2200 s-1. The deformation mechanism of MMCs was evaluated.

Different amounts of TiC particles between 1 and 7.5 vol% were coated on spray-dried B 4 C granules with a simple dry particle coating method, then spark plasma sintered at 2200 °C under vacuum, forming 3D-segregated network structures (SNS) of in-situ TiB 2 between 1 and 9 vol% , to improve the thermoelectric (TE) performance of B 4 C. With the in-situ TiB 2 -SNS, a maximum ZT of 8.02×10−2 was achieved with 2 vol% TiB 2 -SNS at 923 K by simultaneous improvement of electrical conductivity due to the electrically conductive network of TiB 2 and reduction of thermal conductivity due to the increased phonon scattering, improving the ZT of monolithic B 4 C by an impressive ≈ 120%. Higher quantities of TiC addition proved inefficient in improving the TE performance; by forming 9 vol% TiB 2 , ≈ 945% increase in electrical conductivity was achieved; however, the Seebeck coefficient was affected negatively, causing a drastic decrease in the ZT value. [ABSTRACT FROM AUTHOR]

We determined the compactability regularities observed during the cold uniaxial pressing of layered powder green samples, taking into account factors such as composition, height, and number of Ti–B (TiB) and Ti–Al–Nb–Mo–B (TNM) layers. The following composition was chosen for the TNM layer at %: 51.85Ti–43Al–4Nb–1Mo–0.15B, while for the Ti-B layer we selected the composition wt %: Ti-B-(20, 30, 40) Ti. Green samples were made containing both 100 vol % TiB and TNM, and those taken in the following proportions, vol %: 70TiB/30TNM, 50TiB/50TNM, 30TiB/70TNM; multilayer green samples were studied in the following proportions, vol %: 35TiB/30TNM/35TiB, 25TiB/25TNM/25TiB/25TNM, 35TNM/30TiB/35TNM. Based on the obtained rheological data, we determined the rheological characteristics of the layered green samples, including compressibility modulus, compressibility coefficient, relaxation time, and limiting value of linear section deformation. These characteristics were found to vary depending on the composition, height, and number of layers. Our findings revealed that reducing the TNM content in the charge billet composition improves the compaction of powder materials under the given technological parameters of uniaxial cold pressing. Moreover, we observed that increasing the boron content and decreasing the amount of titanium in the Ti–B composition enhances the compactability of powder materials. We also established a relationship between the compaction pressure interval and the density of the layered powder green sample. [ABSTRACT FROM AUTHOR]

Desired ratio of relative permittivity and elastic modulus limits the application of silicone rubbers as flexible electromechanical actuators. The relative permittivity can be improved by incorporating varieties of high‐k (high dielectric constant) particles and polymer reagents as plasticizers and crosslinkers into elastomer matrix. The present work investigates the effect of polyethylene glycol (PEG) flakes, as a soft filler, and titanium diborides (TB) particles, as a hard filler, on electromechanical actuation performance of polydimethylsiloxane elastomer for soft actuator. Elastomer composites with various concentrations of fillers are prepared to compare the influences on optical, dielectric, and mechanical properties. Uniform dispersion of fillers is confirmed by field emission scanning electron microscopy, energy dispersive x‐ray spectrometer, and Fourier transform‐infrared spectroscopy analysis. Results show that the elastic modulus and relative permittivity are significantly influenced by filler contents. The elastic modulus increases with lower concentrations of PEG fillers, and at 8 wt%, it becomes comparable to the base material. Soft fillers aid in maintaining low elastic modulus, whereas hard fillers increase electrical breakdown strength as well as dielectric loss with almost equal changes in relative permittivity for both composites. The maximum actuation strain of 30.8% and 26.2% is attained for an in‐house fabricated linear actuator with 8 wt% of PEG and TB particles, respectively. [ABSTRACT FROM AUTHOR]

B4C-TiB2 composite was synthesized by in situ reaction of TiO2, C, and B4C during vacuum hot pressing. The composition of the composite was varied from 0 to 20 vol.% TiB2. The reaction step was controlled to produce homogenous distribution of TiB2 in B4C matrix with ~ 100% density. The hardness, bending strength, and fracture toughness of B4C monolith and B4C-TiB2 composite were evaluated. B4C-TiB2 composite with 20 vol.% TiB2 content showed 39.4 GPa hardness, 800 MPa bending strength, and 9.8 MPa.m1/2 fracture toughness. The increase in hardness, bending strength, and fracture toughness in B4C-TiB2 composite sample was 29, 56, and 292%, respectively, as compared to B4C monolith. Improvement in hardness and bending strength is attributed to the smaller grain size, i.e., 1.3 µm. The increase in fracture toughness is due to the presence of free carbon at the B4C-TiB2 interface, which creates micro-cracks at the interfacial boundary. [ABSTRACT FROM AUTHOR]

Natural metal composite materials represent a promising class of modern structural materials that need to be welded. Such materials can be welded by fusion, as has been established with the Ti-TiB alloy as an example. The enhanced operational properties of such materials are determined by the microstructure, which is characterized by the presence of microfibers of borides, carbides, or silicides in the metal matrix. To preserve the mechanical properties of materials in a welded joint, it is necessary to ensure the formation of reinforcing microfibers in the welded seam material. Determination of formation mechanism of boride microfibers, originated in the welded seam material, will become the basis for optimizing of fusion welding modes, in particular, electron beam welding mode. The purpose of this study is the determination of formation mechanism of boride microfibers originated in the welded seam material. Two most probable variants of the formation mechanism are analyzed, which involve eutectic decomposition during crystallization from a liquid melt or eutectoid decomposition from a metastable crystallized alloy. The third version is a mixed variant of the two above-mentioned mechanisms. In the article the results of metallographic analysis of features of boride phase distribution and an analysis of elemental composition of boride fibers based on local Auger electron spectroscopy are presented. The object of study was a Ti-TiB alloy joint obtained by electron-beam welding. The analysis factors were the features of size, orientation, and nature of the distribution of boride phase microfibers in different areas of the welded seam. The characteristic elemental composition of boride microfibers, which characterizes the correspondence to equilibrium phases, is also studied. The degree of deviation of the ratio of boron and titanium in such a phase from the thermodynamically equilibrium in different layers of the material of the welded seam, formed by an electron beam in vacuum, is determined. The dependence of boride phase distribution under various conditions of heat exchange in the welded seam material on the side surfaces and in the central regions is established. It is shown that some of boride microfibers formed in the material of the welded seam are characterized by a deviation from the thermodynamically stable composition ТіВn (n = 1) to ТіВn (n = 0.85). The dendritic nature of boride microfibers distribution and the presence of meta-stable phase formations on Ti and B basis provide the grounds for proposing the predominant mechanism for the formation of structure of the welded seam material in the Ti-TiB alloy during crystallization. An analysis of hypothetical variants of the formation mechanism of boride microfibers originated in the welded seam material showed that the formation of a dendritic type of structure is characteristic for the growth of crystals of a new phase in the liquid phase. Such growth is characterized by the formation of equilibrium phases. The presence of a significant amount of non-equilibrium boride phase in the welded seam indicates the residue of non-equilibrium boron in the titanium matrix and continuation of growing of boride fibers in the crystallized welded seam. A determined mechanism for formation of boride microfibers originated in the welded seam material is eutectic decomposition during crystallization from a liquid melt with the formation of TiB microfibers and further growth of such crystals due to eutectoid decomposition from a metastable crystallized Ti-TiB alloy. The results obtained make it possible to understand the mechanism of formation of a welded seam in welded natural-composite metal materials, which permits to develop the recommendations for optimizing the welding technology for such materials.

We studied how the ratio of precursor titanium and boron powders influenced the combustion temperature and combustion velocity in the high-temperature self-propagating synthesis (SHS) mode, and the microstructure, phase composition, and mechanophysical properties of rods fabricated by SHS extrusion. The subject matters of the study were materials for which the as-batch phase compositions of products were TiB–(20–40) wt % Ti. The formation of boron solid solution in titanium was considered. Scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and mechanical measurements implied the texture of the prepared materials (TiB whiskers were aligned in the direction in which the external pressure was applied). In all of the composites studied, the conductivity was close to the conductivity of undoped titanium; the electrical resistance increased slightly in response to increasing boron weight fraction. The three-point bending strength of the material increased by a factor of 1.7 at most as the weight fraction of boron solid solution in titanium increased from 20 to 40 wt %. [ABSTRACT FROM AUTHOR]

AlH 3 is a metastable hydride with a high hydrogen density of 10.1 wt% and it can release hydrogen at a low temperature of 150–200 °C. Many additives (e.g., NbF 5 , TiF 3 , etc.) introduced by ball milling can significantly reduce the decomposition temperature of AlH 3 , but often simultaneously decrease the available hydrogen capacity. In this work, TiB 2 was introduced by ball milling to improve the decomposition performance of AlH 3. AlH 3 + x wt% TiB 2 (x = 2.5, 5, 7.5, 10) composites were prepared by ball milling, and the milling conditions were optimized. It was shown that the decomposition performance of the AlH 3 + 2.5 wt% TiB 2 ball milled at 225 rpm for 108 min is the best. The onset decomposition temperature is 78 °C, which is 60 °C lower than that of pure AlH 3. The decomposition is terminated at 130 °C with 8.5 wt% of hydrogen is obtained. In addition, 5.3 wt% of hydrogen can be released within 200 min at constantly 80 °C. Under the same conditions, ball-milled AlH 3 can hardly release any hydrogen. The activation energy calculated by the Kissinger's method is 86 kJ mol−1, which was 28 kJ mol−1 lower than that of ball-milled AlH 3. Catalytic mechanism study reveals that the Al 2 O 3 layers on the surface of AlH 3 will interact with TiB 2 to form Al–Ti–B solid solution, resulting in lattice distortion. Through lattice activation, the decomposition kinetics of AlH 3 is improved. This work provides an efficient strategy to achieve both high hydrogen capacity and low decomposition temperature of metastable AlH 3 by proper ball milling with metal borides. Both high capacity and low decomposition temperature of AlH 3 were achieved by proper ball milling with TiB 2 which interacts with Al 2 O 3 surface layer to form Ti–Al–B solid solution. [Display omitted] • AlH 3 was properly milled with TiB 2. • Ball milling conditions and TiB 2 content were optimized. • Both high capacity and low decomposition temperature were achieved. • Al 2 O 3 react with TiB 2 to form Ti–Al–B solid solution. • Ti–Al–B solid solution contributes to the improvement of AlH 3 decomposition. [ABSTRACT FROM AUTHOR]

Natural metal composite materials represent a promising class of modern structural materials that need to be welded. Such materials can be welded by fusion, as has been established with the Ti-TiB alloy as an example. The enhanced operational properties of such materials are determined by the microstructure, which is characterized by the presence of microfibers of borides, carbides, or silicides in the metal matrix. To preserve the mechanical properties of materials in a welded joint, it is necessary to ensure the formation of reinforcing microfibers in the welded seam material. Determination of formation mechanism of boride microfibers, originated in the welded seam material, will become the basis for optimizing of fusion welding modes, in particular, electron beam welding mode. The purpose of this study is the determination of formation mechanism of boride microfibers originated in the welded seam material. Two most probable variants of the formation mechanism are analyzed, which involve eutectic decomposition during crystallization from a liquid melt or eutectoid decomposition from a metastable crystallized alloy. The third version is a mixed variant of the two above-mentioned mechanisms. In the article the results of metallographic analysis of features of boride phase distribution and an analysis of elemental composition of boride fibers based on local Auger electron spectroscopy are presented. The object of study was a Ti-TiB alloy joint obtained by electron-beam welding. The analysis factors were the features of size, orientation, and nature of the distribution of boride phase microfibers in different areas of the welded seam. The characteristic elemental composition of boride microfibers, which characterizes the correspondence to equilibrium phases, is also studied. The degree of deviation of the ratio of boron and titanium in such a phase from the thermodynamically equilibrium in different layers of the material of the welded seam, formed by an electron beam in vacuum, is determined. The dependence of boride phase distribution under various conditions of heat exchange in the welded seam material on the side surfaces and in the central regions is established. It is shown that some of boride microfibers formed in the material of the welded seam are characterized by a deviation from the thermodynamically stable composition ТіВn (n = 1) to ТіВn (n = 0.85). The dendritic nature of boride microfibers distribution and the presence of meta-stable phase formations on Ti and B basis provide the grounds for proposing the predominant mechanism for the formation of structure of the welded seam material in the Ti-TiB alloy during crystallization. An analysis of hypothetical variants of the formation mechanism of boride microfibers originated in the welded seam material showed that the formation of a dendritic type of structure is characteristic for the growth of crystals of a new phase in the liquid phase. Such growth is characterized by the formation of equilibrium phases. The presence of a significant amount of non-equilibrium boride phase in the welded seam indicates the residue of non-equilibrium boron in the titanium matrix and continuation of growing of boride fibers in the crystallized welded seam. A determined mechanism for formation of boride microfibers originated in the welded seam material is eutectic decomposition during crystallization from a liquid melt with the formation of TiB microfibers and further growth of such crystals due to eutectoid decomposition from a metastable crystallized Ti-TiB alloy. The results obtained make it possible to understand the mechanism of formation of a welded seam in welded natural-composite metal materials, which permits to develop the recommendations for optimizing the welding technology for such materials. [ABSTRACT FROM AUTHOR]

The work is devoted to the search for new vacuum-plasma coatings with high hardness to increase the durability of the compressor blades of the GTE of aircraft engines Ti-Al-N-based vacuum-plasma coatings obtained by Avinit technologies, which ensure the application of hard, high-quality coatings with dramatically reduced micro-arc damage, were selected as candidates. Avinit multilayer coatings have higher functional characteristics than TiN (microhardness, crack resistance, temperature resistance, erosion and corrosion resistance) and may be promising for applying erosion-resistant coatings for compressor blades. Avinit technologies are technologically closest to the vacuum-plasma technologies used in industrial production for applying TiN protective coatings. New multi-layered 2D nanocomposite wear-resistant ion-plasma hard coatings Avinit (TiN-AlN)n have been developed. The created software products made it possible to reach a qualitatively new level in terms of further modification and improvement of the designs of Avinit functional coatings, stability of technologies and improvement of their quality control when applying such coatings for use in the production of compressor blades of gas turbine engines of aircraft engines. Special attention is paid to methods of preliminary ion-plasma treatment of surfaces before coating. Metallographic studies of the chemical and phase composition and structure of Avinit (TiN-AlN)n coatings have been carried out. The thickness of the coatings is 7–9 μm, the microhardness is 34–35 GPa (compared to the serially used TiN coating: 27.4 GPa). The use of three-stage ion-plasma treatment in Avinit technologies using a double vacuum-arc discharge followed by the application of strengthening coatings in a single technological cycle eliminates the formation of cracks and ensures the production of tightly bonded, high-quality coatings of a given composition with the maximally reduced share of the droplet component. The developed coatings (TiN-AlN)n were applied to experimental batches of working compressor blades of GTE aircraft engines for bench tests [ABSTRACT FROM AUTHOR]

The results of studying the effect of shear deformation and the medium on the phase composition and structure of materials based on Ti–B obtained under the conditions of self-propagating high-temperature synthesis (SHS) are presented. The object of the study was titanium and boron powders in the ratio of 87 wt % Ti and 13 wt % B, which were taken from the calculation to form 70 wt % TiB and 30 wt % Ti during their direct synthesis in the SHS mode. These materials have been synthesized under four conditions: SHS without deformation (i) in air and (ii) helium, (iii) free SHS compression, and (iv) SHS extrusion. It is shown that shear deformation contributes to a more complete course of phase formation processes and uniform distribution of titanium monoboride in the matrix from the Ti[B]x solid solution due to the involvement of the entire volume of the synthesized material in the synthesis process and more uniform heat removal. For each material obtained by these methods, the microstructure has been studied, the quantitative phase composition has been determined, and the crystal lattice parameters of the main TiB phase have been calculated. [ABSTRACT FROM AUTHOR]

In situ TiB-based reinforced composites in the Ti matrix were processed using spark plasma sintering (SPS), and the tribological potential with increasing concentration of B in the composite was explored. Wear and friction tests were carried out at different loads to evaluate the tribological performance of composites prepared by varying the B content 10 at%, 20 at%, and 30 at%, fixing the Fe content. Reciprocating test was used for sliding wear at 10, 15, 20, and 25 N against a counter-body of AISI52100 Steel ball. The presence of beta-Ti, TiB, and FeTi phases was confirmed by X-ray diffraction analysis. Increase in hardness (i.e., 488 to 964 HV0.1) is observed with TiB variation from 13 to 46.8 vol%. 13 vol% TiB shows highest wear and coefficient of friction(COF), while 46.8 vol% B shows the lowest wear and COF at all loads. HR-SEM was used for examination of worn surfaces, which reveals that the wear mechanism is a combination of adhesive, delamination, ploughing, oxidation, and abrasion. [ABSTRACT FROM AUTHOR]

Composites based on boron carbide (B4C) have drawn attention due to their outstanding physical and chemical properties. Herein, the effect of adding boron, titanium, and both titanium and boron, on the B4C‐based material, is investigated. In addition, the additives' influence on the temperature of composite synthesis and the whole sintering process is evaluated. The Ti–B4C composites are prepared by two different methods: pressureless sintering and hot pressing. The presence of Ti, B, and C as dominant additives in the sintered composites is confirmed by X‐ray diffraction and scanning electron microscopy (SEM). The SEM examination reveals that TiB2 particles formed during the composite process synthesis are distributed homogeneously in the B4C matrix. Mechanical properties, such as hardness, Young's modulus, and fracture toughness are tested, along with the composites' density and porosity. All the sintered samples, regardless of the incorporated additives, are characterized by high mechanical properties, reaching outstanding values in a few cases. The obtained results allow us to state that the usage of a boron and titanium mixture significantly improves the sintering process of composites due to the reactive sintering phenomenon occurring during the composites' preparation. The Ti–B4C composites are classified as ultrahigh‐temperature ceramics materials. [ABSTRACT FROM AUTHOR]

Highly dense electrically conductive silicon carbide (SiC)–(0, 10, 20, and 30 vol%) titanium boride (TiB2) composites with 10 vol% of Y2O3–AlN additives were fabricated at a relatively low temperature of 1800°C by spark plasma sintering in nitrogen atmosphere. Phase analysis of sintered composites reveals suppressed β→α phase transformation due to low sintering temperature, nitride additives, and nitrogen sintering atmosphere. With increase in TiB2 content, hardness increased from 20.6 to 23.7 GPa and fracture toughness increased from 3.6 to 5.5 MPa m1/2. The electrical conductivity increased to a remarkable 2.72 × 103 (Ω cm)–1 for SiC–30 vol% TiB2 composites due to large amount of conductive reinforcement, additive composition, and sintering in nitrogen atmosphere. The successful electrical discharge machining illustrates potential of the sintered SiC–TiB2 composites toward extending the application regime of conventional SiC‐based ceramics. [ABSTRACT FROM AUTHOR]

Over the last two decades, many studies have contributed to improving our understanding of the brittle failure mechanisms of boron carbide and provided a road map for inhibiting the underlying mechanisms and improving the mechanical response of boron carbide. This paper provides a review of the design and processing approaches utilized to address the amorphization and transgranular fracture of boron carbide, which are mainly based on what we have found through 9 years of work in the field of boron carbides as armor ceramics. [ABSTRACT FROM AUTHOR]

Searching for microwave absorbers with excellent microwave absorption performance in harsh environments is still a huge challenge. Here, a novel hybrid of TiB 2 plates decorated by multi-layer TiC nanosheets (TiB 2 /TiC hybrids) was fabricated via a molten salt-mediated carbothermal reduction. Due to the increase of the reflective interface, the TiB 2 /TiC hybrids exhibited improved microwave absorption performance with a minimum reflection loss (RL min) value of −52.5 dB (13.1 GHz, 5.2 mm). The reasonable dielectric loss, higher dipole moments and interface effect whereas brought by the three-dimensional multilayer network formed by TiC nanosheets together promoted the improvement of the microwave absorption capacity of TiB 2 /TiC hybrids. [ABSTRACT FROM AUTHOR]

In this work, Ti6Al4V-based composites reinforced with TiB phase are comparatively synthesized by three powder metallurgy approaches: press-andsintering of powder blends; hydrogen assisted 2-stage sintering and sintering of powders preliminary activated by milling procedure. The simplest cold compaction and vacuum sintering of TiH2-based powder blends with Al-V master alloy (MA) and TiB2 powder additives is used as reference approach. It results in the formation of porous Ti6Al4V matrix with inhomogeneous distribution of partially reacted boride phases. Such microstructure is not appropriate to ensure sufficient mechanical characteristics of produced composites. To achieve desirable highly dense composite microstructures with evenly distributed needle-shape TiB reinforcements, two other manufacturing approaches are comparatively tested. Hydrogen assisted 2 stage sintering is based on hydrogenation of not uniform porous composite product obtained after first press-and-sintering cycle, its milling to produce hydrogenated composite powders which are subjected to second compaction and sintering cycle. The alternative approach includes activation milling of HDH-Ti pow-der with TiB2 additives, following blending with TiH2 and MA powders, compaction and sintering operations. Both methods ensure activated sintering of powders, improves density, microstructure uniformity and mechanical characteristics of produced composites compared to reference manufacturing approach. Among all studied manufacturing approaches, Ti6Al4V/TiB composite produced with activating milling of powders exhibits the best mechanical performances owing to combination of reduced porosity, microstructure uniformity and acceptable impurity content. [ABSTRACT FROM AUTHOR]

By the method of x-ray diffraction with a high time resolution, the authors have investigated the phase formation and structuring of titanium borides in the process of SHS with subsequent molding. The evolution of the structure of the material has been shown using the TiB–30 wt.% Ti composition as an example. It has been established that molding occurs due to the formation of an intermediate plastic matrix which serves two functions: the plasticizer and the reactant to form a strengthening phase. Calculations of the adiabatic combustion temperature and of the share of liquid titanium for TiB–Ti compositions with a content of free titanium of 5–80 wt.% have been carried out at temperatures of the original composition of 25–500°C. The processes of molding have been studied for TiB–Ti- and TiB2–Ti-based materials with a content of free titanium of 0–50 wt.% at temperatures of the original composition of 25–500°C. [ABSTRACT FROM AUTHOR]

Innovation in material science progresses the usage of Al2O3/SiC based nanocomposites in gas turbine engine components, the harp-shaped structure of hypersonic rocket engine cutting tools for Ni, Al alloys, and clutch plate for two-wheelers. Thermal stability is one of the significant properties of gas turbine and rocket engine materials. Future engines may have to operate at very high temperature that may require high thermally stable material. In this research, an attempt is made to enhance the thermal stability of the Al2O3/SiC based nanocomposite by reinforcing 5-20 Vol. % nano Titanium Boride. Fabrication of α-Al2O3/SiC with 5-20 Vol. % n-TiB2 was carried out through pressureless sintering at 1600˚C followed by cold compaction. The fabrication process was carried out at a controlled Ar atmosphere. Thermal stability of the sintered samples was analyzed by NETZSCH STA 449F3 thermogravimetric analyzer with a heating rate of 10˚C/min and compared with Al2O3/SiC. The composite α-Al2O3/SiC/(5-20 Vol. %) n-TiB2 showed good thermal stability up to 1488˚C with 6% less mass change than Al2O3/SiC. The addition of nTiB2 enhanced the collaboration between the atoms and postponed the decomposition temperature. The microstructure of the 20 vol % n-TiB2 added α-Al2O3/SiC was captured by 20 kV JSM-5600J Scanning Electron Microscopy and confirmed the presence of n-TiB2. Also, the presence of Ti, Si, Al, O, and B in the nanocomposite was confirmed by energy dispersive analysis of X-beams (EDS). [ABSTRACT FROM AUTHOR]

Aluminium materials are more consumed in the construction and automotive sector for their less corrosion and good machinability. The tribological properties of aluminium can improve while adding reinforcement particles such as Titanium Boride, SiC, Al2O3, etc. This paper investigates the tribological and mechanical characteristics of the Al7075-TiB2 composite to improve its strength and hardness. The TiB2 is reinforced with various ratios like 6%, 12%, 15% for testing purposes. The boride powder was used to preheat up to 830oC with Al7075 for proper mixing. The mechanical properties (tensile and hardness) and metallurgical properties (Wear and Microstructural) are investigated through prepared samples. The composition of Al7075-TiB2 can analyse with the help of the EDAX process. [ABSTRACT FROM AUTHOR]

We present the results of investigation of the specific features of phase-and-structure formation after mechanical activation from the powder charge of a TiH2 –FeSiMn–B4C composite produced by thermal synthesis. The procedure of mechanical activation was carried out in a planetary mill in alcohol for 5; 9; 12, and 18 min. To compare the influence of mechanical activation on the phase-and-structure formation, the same mixture was ground in a ball mill of the "drunken barrel" type. The alloys were thermally synthesized in a vacuum in two consecutive stages: heating to 600°С and further heating to 1250°C. It was established that the role of major phases in the analyzed alloy after low-energy grinding in the ball mill was played by titanium carbide TiC and titanium silicide Ti5Si3 and Ti5Si4 phases. It was discovered that, in the course of mechanical activation of the mixture, the content of titanium carbide decreases, whereas the TiB boride phase appears in the alloy and finally turns into the main phase. It is not reasonable to increase the duration of grinding in the course of mechanical activation of the powder mixture and make it longer than 12 min because this leads to the formation of elevated contents of oxygen compounds. It was shown that mechanical activation also affects the shrinkage of the material. [ABSTRACT FROM AUTHOR]

TiB-reinforced Ti3Al2.5V, in which the TiB whiskers are oriented parallel to the direction of heat extrusion, was fabricated via powder metallurgy. To investigate the effects of TiB whisker volume fraction on fatigue properties in Ti3Al2.5V, four-point bending fatigue tests were conducted on plate-type specimens having TiB whiskers of varying volume fraction and orientation. The fatigue limit and fatigue life of Ti3Al2.5V having TiB whiskers that are oriented parallel to the loading direction tended to be increase with increasing TiB volume fraction, whereas the fatigue limit and fatigue life of specimens having TiB whiskers oriented along the short transverse direction did not depend on the TiB volume fraction. The fatigue limit of specimens with TiB whiskers oriented along the long transverse direction tended to decrease with increasing TiB volume fraction, because fatigue cracks were initiated and propagated along the TiB whiskers. Thus, the resistances of fatigue crack initiation and propagation behavior in Ti3Al2.5V changed with both the TiB volume fraction and orientation. [ABSTRACT FROM AUTHOR]

Ti6Al4V alloy composite coatings in-situ reinforced with TiB-TiN were deposited on Ti substrate using plasma spraying. Influence of plasma power (50 and 60 kW) and deposition speed (40 and 50 mm/s) on coating microstructure and bio-tribocorrosion performance was analyzed. Process parameters found to have strong influence on the tribocorrosion behavior and the material loss/damage of these coatings was found to be significantly less than that of Ti substrate. However, corrosion played a dominant role in affecting the wear and overall damage of all materials. Present in-situ composite coatings reinforced TiB-TiN exhibited superior tribocorrosion resistance than Ti substrate as a result of their high hardness and non-passivating nature. [ABSTRACT FROM AUTHOR]

Al 7075 alloy matrix reinforced with different weight percentage of titanium borides (TiB2, 0, 1.5, 3, 4.5 and 6 wt%) and 1 wt% graphite (Gr) hybrid composites were synthesized by in-situ liquid metallurgy route, then the sliding wear characteristics were performed and investigated in this research work. TiB2 reinforced as 0, 1.5, 3, 4.5 and 6 wt% by the in situ chemical reaction of KBF4 and K2TiF6 salts and 1 wt% Gr with the Al 7075 matrix were added constantly in the melt. Several experiments were carried out to examine the wear behavior of the fabricated composite specimens through a tribometer at ambient temperature. The weight percentage of reinforcement (TiB2 particles), the applied load, the sliding velocity (SV), and the sliding distance (SD) were selected as process parameters at five different levels. The response surface methodology (RSM) was used to conduct the experiments as RSM is the feasible and accurate method employed for optimizing to set the parameters. To check the significance of the developed model by RSM, ANOVA and confirmatory tests were also accomplished. FESEM surface morphology was also carried out to illustrate the uniform dispersion of the TiB2–Gr particulates in Al 7075 matrix. The predicted wear characteristics from the developed model were well agreed with the experimental results. The obtained results were explained that both the increase in the percentage of RF and SV have dropped the wear loss (WL) curve whereas the load at all SVs and the SDs were uplifted the WL. The worn surface morphology explained that the adhesive mechanisms were dominated during the sliding wear test. Further, severe and mild wear occurred during higher load and lower load respectively. [ABSTRACT FROM AUTHOR]

TiB2/Al2O3 ceramics reinforced with MgO are prepared by spark plasma sintering (SPS). The dielectric and microwave (MW) absorption properties are discussed. The results indicate that both the commercial TiB2 (C-TiB2) content and preparing temperature play important roles in the dielectric properties. Simultaneously, TiB2/Al2O3 composite shows the best MW absorption property when the C-TiB2 content and preparing temperature are 9 wt% and 1400°C. To further improve the MW absorption properties, the composite containing 9 wt% synthesized TiB2 (S-TiB2) has been sintered at 1400°C. Its high-temperature complex permittivity is greater than that of TiB2/Al2O3 composite with 9 wt% C-TiB2 sintered at 1400°C and is directly proportional to the temperature. Besides, TiB2/Al2O3 composite with 9 wt% S-TiB2 possesses a better MW absorption at 25–500°C, its effective absorption bandwidth (RL<−5 dB) can reach 4.2 GHz at 25–500°C. And the minimum reflection loss (RLmin) value reaches −43.41 dB at the temperature of 800°C with a thickness of 1.45 mm for TiB2/Al2O3 composite with 9 wt% C-TiB2. Consequently, the satisfying absorbing layer (d<1.75 mm), flexural strength, heat stability and considerable high-temperature MW absorption ability grant TiB2/Al2O3 ceramics practical applications as high-temperature microwave absorption materials (MAMs). [ABSTRACT FROM AUTHOR]

The design of the high-temperature microwave absorbing materials (MAMs) with temperature-insensitive and considerable microwave absorption (MA) capacity is a tremendous challenge. TiB2-Al2O3/MgAl2O4 MAMs are prepared by the spark plasma sintering (SPS). Further, the influences of the Al2O3 content on the flexural strength, thermal stability, high-temperature electrical conductivity, dielectric and MA properties are discussed. The results show that the Al2O3 content is associated with flexural strength, high-temperature thermal stability, electrical conductivity, dielectric and MA properties. Meanwhile, the temperature-insensitive and considerable MA properties with the minimum reflection loss (RLmin) ranging from −19.4 to −14.3 dB and the effective absorption bandwidth (EAB, RL<−5 dB) of 3.19–3.55 GHz are attained at 25°C–700°C in 8.2–12.4 GHz as the Al2O3 content increases from 70.6 wt% to 80.6 wt%. This is ascribed to the compensating effect of the positive and negative temperature coefficient materials on the high-temperature electrical conductivity as well as the co-play of the dipolar and interfacial polarization at elevated temperatures. Consequently, TiB2-Al2O3/MgAl2O4 ceramics exhibit the ideal prospect as the high-temperature MAMs. [ABSTRACT FROM AUTHOR]

The addition of Ti and its compounds particles has the potential to effectively enhance the fracture toughness of B 4 C ceramics. However, the influence of different Ti-based compounds on B 4 C ceramics has not been extensively studied. In this work, B 4 C–TiB 2 multiphase ceramics were prepared by adding 5% Ti or its compounds (TiO 2 , TiB 2 or TiC) in B 4 C and the effects of the additives on the B 4 C ceramics were studied. For this purpose, we adopted a sintering process carried out in situ in the absence of pressure at a temperature of 2250 °C for 1 h. It was evident from the results that the additives are capable of enhancing the sintering densification characteristics and the properties exhibited by B 4 C, as opposed to single-phase B 4 C ceramics. Additionally, different additives have varied effects on the microstructures and mechanical properties of B 4 C–TiB 2 multiphase ceramics. The results of the study indicate that the TiC-added sample exhibits the most optimal mechanical properties, with 4.52 MPa m1/2 fracture toughness, 344.0 MPa flexural strength, 26.2 GPa hardness, and 516.0 GPa elastic modulus. [ABSTRACT FROM AUTHOR]

TiB 2 –MgO microwave absorbing materials with TiB 2 as the absorber, MgO as the matrix are prepared by spark plasma sintering (SPS). The influences of commercial TiB 2 content and sintering temperature on dielectric and microwave absorption (MA) properties are studied. Besides, to optimize the MA performance, TiB 2 –MgO composite containing TiB 2 synthesized by the carbonthermal process is prepared. Meanwhile, its high-temperature dielectric and MA properties are investigated. Indeed, both the commercial TiB 2 content and sintering temperature play key roles in dielectric and MA properties, as they reaching 8 wt% and 1400 °C, the composite presents the optimal MA performance. For composite with synthetic TiB 2 as the absorber, the temperature has a positive effect on dielectric and MA properties. The enhanced high-temperature MA properties with minimum reflection loss (RL min) of −52.11 dB at 1.6 mm under 500 °C and effective absorption bandwidth (EAB, RL < −5 dB) of 4.2 GHz at 1.4–1.6 mm under 800 °C are obtained, which is mainly attributed to the temperature-dependent interfacial polarization compared to the temperature-insensitive conductivity. The excellent mechanical properties (flexural strength = 212.48 MPa), thin absorbing layer (d < 2 mm), enhanced thermal stability and high-temperature MA properties indicate that the TiB 2 –MgO composites can be considered as new candidates for high-temperature structure microwave absorbing materials. [ABSTRACT FROM AUTHOR]

To obtain a significantly higher Young’s modulus than conventional wrought steels, the improvement of the sintered density was necessary for low-alloyed sintered steels containing 15 vol% or more TiB2. In this study, the effect of boride powders as the small amount additives on the sintered density and the Young’s modulus of TiB2 reinforced low-alloyed sintered steels was investigated. A small amount addition of ZrB2 powder was suitable to increase the sintered density of low-alloyed sintered steels containing 15 vol% or more TiB2, because of promoting the infiltration of the liquid phase formed during sintering into the agglomerates of TiB2 particles. As a result, the high sintered density equivalent to 97% of pore free density and the high Young’s modulus of 300 GPa equivalent to 1.5 times that of conventional wrought steels were achieved when the content of TiB2 was 40 vol%. [ABSTRACT FROM AUTHOR]

Titanium–titanium boride (Ti/TiB) metal matrix composites have been widely identified as promising materials for various applications. The traditional ingot metallurgy processing strategies used to fabricate these materials are energy intensive and have fallen short of their perceived mass production potentials. Powder metallurgy processing, especially that aimed at in-situ synthesis of Ti/TiB composites from titanium and TiB2 powder blends, is currently widely used for the cost-efficient production of such composites. However, this approach usually results in excessive sintered porosities and associated mechanical property degradation. Therefore, further thermomechanical or hot isostatic pressing steps are required for porosity reduction. In the present study, low-porosity Ti/TiB composites were synthesized using TiH2 and TiB2 powders via a simple press-and-sinter hydrogen-assisted blended elemental powder metallurgy route. The manufacturing route included two stages. Compaction and vacuum sintering of the noted blended powders was followed by hydrogenation and ball milling of the pre-sintered product to produce a hydrogenated, pre-alloyed powder. This was followed by compaction and final sintering. X-ray diffraction, light microscope, and scanning electron microscope were employed to investigate the powder morphology and material microstructures after various processing steps. The role of temporary alloying with hydrogen was established in tailoring the microstructure. When an optimized particle size distribution that was carefully controlled using a Malvern Mastersizer laser analyzer was combined with optimized hydrogenated pre-alloyed Ti/TiB powder compaction and sintering parameters, a nearly dense, uniform composite was formed. The above approach can be considered a promising solution for economical manufacturing of Ti/TiB parts with improved properties, such as a high performance-to-cost ratios.

Possibilities of obtaining and using an intermediate layer for joining of Ti-TiB and austenitic steel 12X18H10T (analog of AISI 321; 1.4541; X10CrNiTi18-10) were studied. An alloyed interlayer with TiB reinforcing fibers and the main alloying elements of 12X18H10T steel was formed on the surface of the Ti-TiB sample. Such interlayer was formed during electron beam welding of Ti-TiB with vanadium using foil made of 12X18H10T steel. The microstructure of the interlayer consists of a metal matrix reinforced with microfibers. It’s composition corresponds to vanadium-alloyed titanium boride. In comparison to the initial Ti-TiB alloy, significant grinding of reinforcing boride microfibers in the interlayer microstructure was observed. Besides, the phase formations close to Ti2B in zone of primary titanium borides decomposition in the interlayer, initiated by electron beam were determined. As a result, application of Ti (63-68 at.%) and V (18-25 at.%) based interlayer with alloying additives (Fe, Cr, Ni, B, C) has great potential for utilization in electron-beam welding of 12Х18Н10Т steel with Ti-TiB alloy.

The basic regularities and ways of optimizing the production of welded joints of Ti – TiB alloy plates and 12Х18Н10Т steel were studied. The ways to achieve the necessary mechanical characteristics of welded structures from elements with a thickness of 10 mm obtained by electron beam welding were found out. It was determined that electron beam welding of Ti – TiB alloy compounds with 12Х18Н10Т steel is effective when using a double strip of niobium and 10Г2 steel. It was found that in order to obtain welded joints of the Ti – TiB alloy with Nb electron beam welding, it is necessary to ensure the melting of the Ti – TiB alloy, conditions for wetting niobium with the obtained melt, and to prevent the formation of an intermetallic layer in the weld. It is shown that the welded joint Ті-TiB - Nb - 10Г2 - 12Х18Н10Т obtained by electron beam welding allows to achieve a strength level of at least σв = 260 MPa.

The effect of TiB2 additions on the structure, phase composition, and mechanical and tribological properties of materials in the Fe–FKh800 system was studied. The introduction of titanium boride additions activated compaction of the iron-based composites through sintering with participation of the liquid phase that emerged with the formation of low-melting Fe–C–B (Tm ~ 1050°C) and γ-Fe–Fe2B–TiB2 (Tm ~ 1162) eutectics and led to a 50–70°C decrease in the sintering temperature of the compacts. Titanium boride additions between 0.38 to 0.74 wt.% provided 20–25% higher bending strength of the 65 wt.% Fe–35 wt.% FKh800 composite with a slight increase in hardness. Metallographic studies, X-ray diffraction, and electron microprobe analysis of the Fe–35 wt.% FKh800–TiB2 materials showed that titanium boride additions promoted a multiphase, microheterogeneous matrix-reinforced composite, consisting of Kh17 chromium steel, double M7C3 and M3C iron–chromium carbides, and complex Me3(CB) carboborides. The influence of TiB2 additions on the wear resistance of the composites subjected to dry friction against fixed diamond wheel particles and ShKh15 steel was studied. The study showed that the abrasive mass wear (Im) of carbide steels decreased from 36.94 to 14.8 mg/km and their linear wear (Il) decreased from 0.197 to 0.079 mm/km with TiB2 additions increasing from 0.38 to 1.48 wt.%. Titanium boride additions ranging from 0.38 to 2.2 wt.% reduced the mass wear rate from 4.9 to 1.9 mg/km in dry friction of the composite against a ShKh15 steel counterface with 50–55 HRC hardness and decreased the friction coefficient from 0.49 to 0.38. [ABSTRACT FROM AUTHOR]

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Copyright of Nanosistemi, Nanomateriali, Nanotehnologii is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

[Display omitted] • Superhard TiB coating on Ti by high power diode laser alloying of amorphous boron. • Laser alloying of amorphous B with Ti resulted in TiB 2 dendrites and TiB whisker microstructures. • High hardness of 3800–4700 HV 0.2 and 800–1600 HV 0.2 in alloyed of 1 mm. • Gibbs free energy of formation shows a high negative values for TiB 2 and TiB. • 4-fold decrement in wear rate due to titanium boride phase formations. Present work deals with fabrication of superhard titanium boride coating on titanium surface with preplaced amorphous boron layer using high power diode laser alloying. Amorphous boron instantaneously converts into crystalline boron by the effect of high-power laser interaction, which rapidly drives the boron species into titanium liquid pool and form titanium boride precipitates by its convective flow. Negative Gibbs free energy (ΔG) and enthalpy (ΔH) of amorphous boron crystallization reaction introduces the concept of laser induced self-propagation synthesis. Gibbs free energy (ΔG) for the chemical reactions between Ti and B was calculated to confirm the spontaneous formation of titanium boride compound phases. The diffusion coefficient and activation energy were estimated to understand the phase formation and microstructural evolution. The structural phase, microstructure, microhardness and wear resistance of the laser borided titanium was investigated by XRD, optical and scanning electron microscopy, EDAX, Vickers microhardness analysis and linear reciprocating wear testing. The laser alloyed coating across the cross section shows formation of dendrites and whisker like microstructures. Average microhardness of 800–1600 HV 0.2 was measured at different cross-sectional depths and an extreme hardness of about 3800–4700 HV 0.2 was obtained in some regions of boron precipitates. The results showed a high negative value of Gibbs free energy of about −250 kJ/mol and −170 kJ/mol at ∼2000 °C respectively which confirms the spontaneity of TiB 2 and TiB phase formation. The activation energy of the titanium boride is estimated to be 140 kJ/mol. The laser borided coating with the formation of TiB and TiB 2 phases could be useful for surface engineering applications. [ABSTRACT FROM AUTHOR]

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ZrB2‐SiCw ceramic sheets produced by tape casting and tailored ductile Ti foil were alternatively stacked and sintered by spark plasma to synthesize a multi‐layered ceramic. Following mechanical processing, a high flexural strength (621 MPa) and fracture toughness (15.3 MPa·m1/2) in uniaxial tension were achieved in comparison to laminated ceramics with a weak BN interlayer. Scanning and transmission electron microscopy revealed a characteristic macroscopic heterogeneous lamella as well as a three‐tier microstructured interface, termed the L‐T structure. This novel structure provides a new path for the development of ceramic/metal layered composites with superior mechanical properties in the near future. [ABSTRACT FROM AUTHOR]

In order to produce ceramic composites having both high Vickers hardness Hv ≥20 GPa and high fracture toughness KIC ≥10 MPa·m1/2, dense TiB2/[ZrO2-Al2O3] composites have been fabricated using pulsed electriccurrent pressure sintering (PECPS) at 1873 K under 50 MPa for 6.0 × 10² s in Ar. As the former starting materials, two kinds of TiB2 powders were adopted; i) mono-modal particle size (Ps) distribution with an average particle size s> of 3.24 μm and ii) bi-modal Ps distribution with s> of 3.06 μm, composed of the small Ps of 0.58 and the large Ps of 3.27 μm. On the hand, the latter was the mixed powders composed of ZrO2(2.5 mol%Y2O3) solid solution (ss) and α-Al2O3 powders: each primary Ps was 0.1~0.2 μm. Thus fabricated composites consisting of TiB2, tetragonal/monoclinic ZrO2 and α-Al2O3 with relative densities more than 99.0% showed improved mechanical properties, especially bi-modal TiB2/[ZrO2-Al2O3] composites revealed high Hv of 22.3 GPa and KIC of 12.8 MPa·m1/2. These high-mechanical behaviors might be explained in terms of i) better powder particle configuration, ii) high chemical stability of TiB2, iii) the most proper composition, with adoption of iv) bi-modal TiB2 powder and v) the most suitable sintering condition. [ABSTRACT FROM AUTHOR]

Powders of TiO2 mixed with TiB2 of mmol% (m = 0, 1, 2, 3, 4, 5, 10, 12, 20) were prepared, and sintered by using an spark plasma sintering apparatus, the chemical reaction between TiO2 and TiB2 in the sintering process was investigated. In the case of m = 2 to 20, it was found TiO2 was reduced by TiB2, to form and the Magneli phases (TinO2n−1 (n = 3, 4, 5, 6)). The maximum value of the dimensionless figure of merit ZT was 0.18 at 800°C for m = 3, and almost the same value as that of the TiO2-TiN sintered bodies was obtained. The effective carrier concentrations in the TiO2-TiB2 sintered bodies were estimated from Heikes’s formula was about 2.4 times larger than those of the TiO2-TiN, TiO2-TiC, TiO2-VC sintered bodies. The electron mobility μ tends to increase as m increases. The thermal conductivity was dominated by the lattice thermal conductivity at m = 0, while the electronic thermal conductivity was suggested at m = 4 and 5. It was confirmed that the formation of the magneli phase contributes to the improvement of ZT. [ABSTRACT FROM AUTHOR]

A CALPHAD-guided alloy design strategy is used here to design and process fully dense titanium boride (TiB) ceramic alloys containing a ductile phase for toughening. This involved the construction of high temperature phase fields of the Ti-B-Fe-Mo quaternary alloy system using the CALPAHD approach. To design the compositions, ternary phase diagrams of Ti-B-Fe, Ti-B-Mo, and Fe-Mo-B systems were first constructed using the thermodynamic databases that were verified to predict well the binary phase diagrams of components. Using this as a basis, the pseudo-ternary diagrams of the Ti-B-Fe-Mo system were constructed to map the high temperature phase fields over a wide range of composition. This made it possible to identify relatively lower reaction sintering temperatures for various alloy compositions. Two compositions of TiB ceramic alloys with the ductile beta-phase (both having ∼85% TiB and ∼15% β-Ti phase), were considered for the demonstration of the present approach. Based on the pseudo-ternary phase fields, these two compositions could be processed using electric-field-activated sintering (EFAS), in a relatively short time, at their respective liquid-phase-forming temperatures. The processing temperature was as low as 1423 K for a Fe/Mo-rich ceramic alloy composition, but the formation of brittle intermetallic phase FeTi here was found to be detrimental to mechanical properties. The second TiB ceramic alloy composition, which was Fe/Mo-lean, could be processed at 1623 K. This composition is shown here to possess a very good combination of high flexural strength (∼850 MPa) and high fracture toughness (∼7.7 MPa√m), making it attractive for potential applications. The identification of the liquid phase reaction sintering regions in the ternary phase diagrams, and the eventual finding of one composition giving a relatively high strength and toughness, demonstrate that this is an effective approach for alloy design. The microstructural factors that control the strength and toughness have been identified and the ways to increase these properties further, in this class of materials, are suggested. Image 1 [ABSTRACT FROM AUTHOR]

Highlights • The SS/TiB 2 /Al 2 O 3 solar absorber coating has been prepared. • The coating exhibits a high absorptance of 0.93 and a low emittance of 0.11. • The coating exhibits a good thermal stability at 700 °C for 2 h and 600 °C for 100 h in vacuum. • The chromaticity diagram of the coating with respect to annealed temperatures is established. Abstract Transition metal titanium diboride (TiB 2) is a promising material for the solar selective absorbing coatings due to its favorable spectral selectivity and thermal stability. In this research, spectrally selective TiB 2 /Al 2 O 3 tandem absorber is deposited on stainless steel (SS), which exhibits a high solar absorptance (α s = 0.93) and a low thermal emissivity (ε = 0.11). In this tandem absorber, the TiB 2 acts as the main absorber layer and the Al 2 O 3 acts as an antireflection layer. The tandem absorber coating is systematically characterized by ultra-high resolution scanning electron microscope (SEM), UV–vis-NIR spectrophotometer, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and Micro-Raman techniques. The thermal stability in vacuum of the SS/TiB 2 /Al 2 O 3 tandem absorber coatings is investigated in the temperature range of 400–800 °C for 2 h and 100 h, respectively. SEM and Raman spectra indicate that the change of surface morphology and chemical composition for the coating result in the degradation of optical performance. With the different annealed temperature, the SS/TiB 2 /Al 2 O 3 tandem absorber coatings exhibit different color, which is further investigated using chromaticity diagram. [ABSTRACT FROM AUTHOR]

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In this study, in order to evaluate the electrochemical performance of different titanium boride coatings created on the commercially pure titanium (CP-Ti), distinct electrochemical assays in Hanks' balanced salt solution at 37 °C were conducted using pack cementation method. The results showed that the boriding at 900 and 1000 °C for 3 h creates the TiB whiskers and TiB whiskers/TiB2 dense layer on the top of the commercially pure titanium surface, respectively. It was also found that not only borides coating had good adhesion on the substrate, but also that improved the titanium hardness more than five times. Polarization plots clarified the passive behavior of borided specimens. Impedance spectroscopy tests indicated the acceptable corrosion behavior of the borided specimens in Hanks' balanced salt solution. Mott-Schottky measurements indicated that the passive layers formed on the commercially pure titanium and the borided specimens had doped n-type semiconductor properties. Mott-Schottky measurements displayed that the donor density of the passive layers decreased with the rising time as well. Finally, because of better surface conditions to make a less defective and more protective passive layer, the borided specimen at 900 °C in comparison with the borided specimen at 1000 °C was shown to be the more suitable choice for bioimplant applications. [ABSTRACT FROM AUTHOR]