Amount Of TiB2 Research Articles

Gradient Coating of Laser Cladding TiB2/Ti-Based Alloy on Titanium Alloy Surface

The technology of the TiB2/TiB cladding layer addresses the issue of the insufficient wear resistance of cup-shaped parts composed of titanium alloy materials. In order to eliminate the cracking problem of laser cladding TiB2/Ti-based alloy, 30%TiB2/Ti-based alloy gradient coating was prepared on the surface of titanium alloy by laser cladding in this study. The results revealed that the microstructure of the matrix and the cladding layer is metallurgically bonded. The microstructures of the cladding layer appear as rod-like and coarse-grained features on the surface, and fine needle-like and small-grained morphologies inside. The fine needle-like TiB precipitated in situ from the melt has a flat interface with Ti and exhibits a low degree of interfacial mismatch, while the interface between small particle-like TiB and Ti is wavy and has a high degree of interfacial mismatch. The gradual increase in the amount of TiB is present from the surface to the bottom of the cladding layer, while the amount of unmelted TiB2 particles decreases. The chemical structure of the cladding layer is mainly presented as TiB2, TiB and α-Ti phases. The maximum hardness of the cladding layer is 725 HV0.2, where it is more than twice the hardness of the substrate. The fretting wear resistance of the cladding layer is better than that of the titanium alloy substrate under low loads (50 N–100 N), while a high load (more than 150 N) triggers a reverse outcome.

Microstructure and mechanical properties of medium-entropy TiNbZr alloy-based composites, reinforced with boride particles

The TiZrNb metal-matrix composites reinforced by in-situ formed borides were produced by vacuum arc melting using different amount of TiB2 (0.2, 2.0 and 4.4 wt%). Structure, mechanical properties and biocompatibility of the composites were studied. The initial microstructures of the composites were composed of the bcc TiZrNb matrix and needle-like (Ti, Nb) B particles the volume fraction of which was ∼ 1.0%, 6.8% and 13.2%, respectively. Besides a small amount of the ω phase particles measuring ∼ 10 nm were found in the matrix of all the composites. Compression test at room temperature showed that the minimum content of the borides did not have noticeable strengthening effect on mechanical properties of the composite. An increase in the amount of (Ti, Nb) B to 6.8 vol% resulted in an increase in the yield stress by 22% to ∼ 900 MPa without a visible decrease in ductility. The composite with 13.2 vol% of the borides showed the yield strength of 1010 MPa and compression ductility (deformation till fracture) of 9% that can be associated with a hypereutectic composition and appearance of coarse particles of primary (Ti, Nb) B. Evaluation of main strengthening mechanisms suggested that the load transfer strengthening contributed mainly to the overall strength of the composite. Analysis of biocompatibility suggests some decrease in the proliferation rate of mesenchymal stem cells with an increase in the borides amount.

Microstructure and properties of bilayered B4C-based ceramics

Bilayered B4C-based ceramics were obtained by hot-pressing. Microstructure, mechanical and ballistic properties of the bilayered ceramics were investigated. One layer was obtained upon addition of Ti and C to the hard B4C matrix, the newly formed TiB2 phase uniformly distributed in the matrix. The other layer included variable amounts of Ti3SiC2, equal to 10, 20, 30, 40 wt%, and the B4C-SiC matrix in a fixed weight ratio of 7:3. The amount of TiB2 and SiC phases, deriving from Ti3SiC2 decomposition upon sintering, increased with increasing the Ti3SiC2 content. The flexural strength and fracture toughness of bilayered ceramics both increased with increasing the Ti3SiC2 content from 10 to 40 wt%. Ballistic testing showed that the B4C-based ceramic target containing 30 wt% Ti3SiC2 broken into pieces upon being impacted by a 12.7 mm armor-piercing incendiary (API) projectile, and effectively consumed the bullet energy and protected the backing plate from serious damage.

Mechanical Properties and Microstructures of Al2O3/TiC/TiB2 Ceramic Tool Material

In order to develop a new ceramic tool material with self-repairing capability, Al2O3/TiC/TiB2 ceramic tool material was prepared by vacuum hot-pressure sintering method. The toughening and strengthening mechanism of TiB2 on Al2O3/TiC substrate was analyzed. The results show that the ceramic tool material has good comprehensive mechanical properties when the TiB2 content is 10 vol.%. Its flexural strength was 701.32 MPa, hardness was 18.3 GPa, and fracture toughness was 6.2 MPa·m1/2, which were improved by 11.6%, 2.2% and 16.1% respectively, compared with the Al2O3/TiC tool material. Fracture surfaces of the Al2O3/TiC/TiB2 ceramic tool material were characterized by SEM, EDS and XRD. The results showed that the fracture mode was a mixture of transgranular fracture and intergranular fracture. The growth of Al2O3 and TiC grains can be effectively inhibited by adding appropriate amount of TiB2, and the internal grains of the material can be refined. The TiB2 has a uniform distribution in the matrix and acts as a diffusion toughening agent. The cutting performance of Al2O3/TiC/10 vol.%TiB2 tool material was further investigated. Experiments conducted on tools made of Al2O3/TiC and Al2O3/TiC/TiB2 materials showed that the main forms of wear for both tools were abrasive wear and bonded wear. The friction coefficient of Al2O3/TiC/TiB2 tools was reduced by 10.77% compared to Al2O3/TiC tools.

Brazing of (TiB + Y2O3) reinforced titanium matrix composites using CuTiZrNi amorphous filler alloy

(TiB + Y2O3)/titanium matrix composites (TMCs) were brazed with CuTiZrNi amorphous filler alloy. The joint showed integral interfaces without any imperfections. The joint brazed at 900 °C can be divided into 2 zones. Microstructure of zone I was demonstrated as (Ti,Zr)2(Cu,Ni) + α-Ti + TiB and zone II was a continuous TiCu reaction layer. Higher temperature accelerated the elemental diffusion between the joint and substrates, thickened the brazing seam and TiCu layer diminished when brazed at 980 °C. The amount and size of (Ti,Zr)2(Cu,Ni) phase decreased while the amount of TiB and Y2O3 phase increased with increasing brazing temperature. When brazing temperature rose higher than 980 °C, the joint was occupied by reticulation-distributed (Ti,Zr)2(Cu,Ni) + α-Ti eutectic structure. At higher brazing temperatures, TiB was greatly refined as the decomposition of the original TiB enhanced and more reconstructed TiB precipitated during cooling. The joint shear strength increased greatly with increasing brazing temperatures and reached the maximum of 646.0 MPa when brazed at 1020 °C. Further increasing the brazing temperature to 1060 °C, the joint strength did not change obviously. The fracture locations changed when brazed at different temperatures. The joints at different parameters showed cleavage fracture or quasi-cleavage fracture.

Microstructural characteristics and evolution of in situ xTiB2/Al-20%Si alloy

xTiB2/Al-20%Si composite is a hypereutectic Al-20Si alloy containing x wt% TiB2 sub-micron or nanometre level in situ particles. The xTiB2/Al-20%Si composites were prepared using an 11% TiB2/Al-6Si composite as the master alloy. The phases and microstructures in the composites were evaluated by use of XRD, OM, SEM, EDS, EPMA, and TEM. The microstructural evolution of the Al-20Si alloy with the addition of TiB2 particles from 1 wt% to 6 wt% was investigated. The results showed that the primary Si, α-Al phase, and eutectic Si could be refined and modified by TiB2. Meanwhile, the crystal structures of Ti-B compound enwrapped by primary Si and α-Al phase were identified and analysed and found to form a close-packed hexagonal structure. Compared with the microstructures of composites containing different amounts of TiB2, the TiB2 particles played an important role in the nucleation of primary Si and the growth of primary Si, eutectic Si, and α-Al phases, also explaining the mechanism underpinning the effect of TiB2 on the nucleation and growth of Si and α-Al phases.

Hybrid Ti matrix composites with TiB2 and TiC compounds

Spark plasma sintering method was utilized to produce monolithic Ti and four composite samples with different amount of TiB2 and TiC as additives. The Sintering conditions of 1200 °C for 5 min under 50 MPa external pressure was employed for SPS process. The effect of different amount of additives was studied on the relative density, microstructure and mechanical characterizations of as-sintered samples. Microstructural investigations, thermodynamic assessments and XRD analysis revealed the formation of in-situ TiBw phase in the Titanium matrix composites (TMCs). However, thanks to the short dwell time and existence of coarse TiB2 particles, some semi reacted titanium diboride surrounded by TiBw phase remained into the samples specially the ones with high TiB2 contents. On the other hand, Titanium also diffuse into the TiC phase and the new phase of TiC1-x was produced. The best relative density of 99.77 was obtained for monolithic sample. Adding additives decreased the UTS, elongation and bending strength of as-sintered samples whilst the hardness of specimens increased with addition of more TiB2/TiC. The fractographs shown the role of additives on obtaining a finer microstructure by hindering the extensive grain growth. Predominant fracture mode was brittle and adding more additives rose up the transgranular fractures.

Mechanical and Wear Behaviour of Hot-Pressed 304 stainless Steel Matrix Composites Containing TiB2 Particles

In the present article, mechanical and wear behaviour of hot-pressed 304 stainless steel matrix composites containing 2 and 4 vol% TiB2 particles was investigated. A density of over 92% was achieved at optimum hot-pressing temperature and TiB2 particles’ content. Microhardness and yield strength of the composites were found to be improved remarkably as compared to their unreinforced counterpart. The enhancement of mechanical properties of the composites was discussed in light of their microstructural aspects and different possible strengthening mechanism models. Taylor strengthening was found to be dominant strengthening mechanism as compared to Orowan strengthening and load-bearing effect. Dry sliding wear behaviour was also investigated under load of 35 N at sliding speed 0.3 m/s. The wear resistance of the composites was found to be improved owing to uniform distribution of hard TiB2 particles. Based on our findings, it was concluded that processing parameters and amount of TiB2 have significant influence on mechanical and wear behaviour of steel matrix composites.

Precipitation of iron-rich intermetallics and mechanical properties of Al–Si–Mg–Fe alloys with Al–5Ti–B

ABSTRACTEffects of added Al–5Ti–B master alloys on precipitation of iron-rich intermetallics and mechanical properties of A356 cast alloys with high Fe content (1.5 wt-%) were investigated using image analysis, scanning electron microscopy, and tensile testing. Results show that added Al–5Ti–B has apparent refinement on α (Al) grain size of A356 alloys that have high Fe content. 12 wt-% Al–5Ti–B is beneficial for improving mechanical properties of A356 cast alloys with high Fe content. Improved mechanical properties can be attributed to refined microstructure, the proper amounts of TiB2 and Ti(AlSi)3, and decreased porosity. An excessive amount of Al–5Ti–B deteriorates mechanical properties of alloys because it leads to the formation of large secondary intermetallics and increased porosity.

Mechanical Alloying and Hot Pressing of Ti-Zr-Si-B Powder Mixtures

This work discusses microstructure evolution during ball milling and hot pressing of Ti-xZr-10Si-5B (x = 2 and 5 at. %) and Ti-xZr-20Si-10B (x = 5, 7, 10, 15 and 20 at. %) powder mixtures. Mechanical alloying was carried out in a ball mill using stainless steel balls and vials, 300 rpm and a ball-to-powder ratio of 10:1. Powders milled for 600 min were then hot-pressed (25 MPa) under vacuum at 1100 °C for 60 min. As-milled and hot-pressed samples were evaluated by X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and energy dispersive spectrometry (EDS). Peaks of Si and Zr disappeared in powders milled for 60 and 180 min, respectively, while the lattice parameters and cell volume of α-Ti were varied during ball milling up to 300 min indicating that supersaturated solid solutions were achieved. Ti6Si2B dissolving up to 10 at. % Zr was found in microstructure of hot-pressed Ti-xZr-10Si-5B (x = 2 and 5 at. %) and Ti-xZr-20Si-10B (x = 2, 5, 7 and 10 at. %) alloys. The amount of TiB and Ti5Si3 was preferentially increased whereas the Ti3Si formed in microstructure of the hot-pressed Ti-15Zr-20Si-5B and Ti-20Zr-20Si-10B alloys.

Properties of an Al/(Al2O3+TiB2+ZrB2) hybrid composite manufactured by powder metallurgy and hot pressing

The properties and microstructure of an Al/(Al2O3 + TiB2 + ZrB2) hybrid composite made by using hot pressing of aluminum combined with different amounts of TiB2, ZrB2, and Al2O3 powders are studied. The mechanical properties of the composites are investigated on the basis of microhardness and compression tests. The results show that the microstructure of the composites is uniform and the particles are well distributed in the matrix.

Effect of TiB2 content on the characteristics of spark plasma sintered Ti–TiBw composites

Spark plasma sintering (SPS) was employed to fabricate monolithic titanium and in-situ formed TiB whisker (TiBw) reinforced titanium matrix composites (TMCs) by adding different amounts of TiB2 as boron source. The sintering process was completed at 1050°C for 5min under 50MPa. The influences of TiB2 content (0.6–9.6wt. %) on microstructural evolution and mechanical properties of TMCs were investigated. Thermodynamics, XRD analysis and microstructural investigations confirmed the in-situ formation of TiBw in the composite samples. However, some semi-reacted TiB2 phases, surrounded by TiB coronas, were remained in the microstructure due to the unfinished chemical reaction between the components during a short-time sintering process. The results showed that all samples were appropriately densified by SPS process into the almost dense parts with relative density no less than 97.5%. While bending strength decreased and hardness increased with increasing TiB2 content, the sample with 4.8wt. % TiB2 had the maximum tensile strength. Fractographical assessments showed that the addition of TiB2 hindered the grain growth of titanium matrix. With increasing TiB2 content, fracture mode changed from a multiple pattern to a predominantly transgranular and brittle state.

Dry Sliding Wear Behavior of Aluminum 6063 Composites Reinforced with TiB<sub>2</sub> Particles

The influence of titanium diboride (TiB2) loading on the dry sliding wear characteristics of aluminum 6063 matrix alloy-titanium diboride (Al/TiB2) composite materials has been assessed using a pin-on disc wear tester at different loads. The composites with 5 and 10 wt% of fine TiB2 particles were fabricated using stir casting technique. For comparison, as-cast of the base alloy were made under the same processing applied for Al/TiB2 composites. The hardness of the composite materials was measured using Brinell hardness tester. Scanning electron microscopy (SEM) was used to analyze the wear surfaces of samples. The results indicate that fine TiB2 particles markedly improved the wear performance of the aluminum 6063 matrix alloy. The coefficient of friction decreases with increase in the amount of TiB2, but this effect was more pronounced in dry sliding. Hardness of composites increased with increasing TiB2 loading. The wear rates increase with increase in load and dependent upon TiB2 loading in the base alloy. Among the composites tested, Al/TiB2 composites containing 10 wt% TiB2 exhibited superior wear resistance over the base alloy and 5 wt% Al/TiB2 composites. These observations were correlated in terms of the TiB2 loading in base alloy which resulted in the variations of the hardness.

Synthesis of TiC–TiB–TiB2 composite powders by solid reaction of powders

In the present work, TiC–TiB–TiB2 diffusion-layer-coated B4C composite powders were synthesised via a powder immersion method using Ti and B4C powders as reactants. The phase compositions and microstructure of the treated powders were characterised by employing X-ray diffraction and scanning electron microscopy. No significant reaction between B4C and Ti could be detected at 800°C. After treatment at 900°C, the products generated were composed of TiC and TiB. After treatment at 1000°C, the products generated were primarily composed of TiC and TiB, with a small amount of TiB2. The composition and proportions of the produced phases varied with process temperatures and the composition of the initial powders used. Powder mixtures with a Ti/B4C molar ratio of 3.5:1 and treated at 1000°C for 14 h were more suitable for synthesis of TiC–TiB–TiB2-coated B4C composite powders.

Wear Properties of Metal Matrix Composite Al-Cu and Al-Cu-TiB<sub>2</sub>

Tensile and wear properties of aluminium (Al) based metal matrix composites (MMCs) was prepared by added titanium diboride (TiB2) with in-situ technique by salt route. The salts used in this research were potassium hexafluorotitanate (K2TiF6) and potassium tetrafluoroborate (KBF4). Nanocomposite samples were prepared by casting technique associated with incorporating 3 and 6 wt.% of TiB2 into matrix of Al-6wt.%Cu. Instron and wear tests machine were used to characterize the tensile and wear Al-Cu alloys properties. Results showed that increase in TiB2 content gave the high properties of tensile and wear behavior. The study indicates that TiB2 particles have giving improvement the wear performance of the Al–6wt.%Cu alloy. For a constant load and sliding speed, the wear rate decreases as a function of amount of TiB2 in the composite. The wear rate decrease with increasing in wt.% TiB2 particles for the all loads applied. However, addition of TiB2 particle to the Al–6 wt%.Cu matrix has show the coefficient value of wear decreases regardless of applied load. Study of the wear surfaces both alloy and composites by optical microscope suggests that the improvement in wear resistance is mainly due to the formation of finer groove or debris by content of TiB2.

Reaction synthesis of ultrafine titanium diborides and nitrides reinforced steel matrix composites in situ by spark plasma sintering

A novel technique for synthesis of in situ titanium diborides and nitrides reinforced steel matrix composite (TiB2–TiN/Fe) was put forward. In situ TiB2–TiN/Fe composite was synthesised by spark plasma sintering of mechanically mixed ferrotitanium and boron nitride (BN) powders. The phase evolution during sintering indicates that the TiB2–TiN reinforcements are formed in situ as follows: first step, the solid/solid interface reaction between ferrotitanium and BN, resulting in the formation of a small amount of TiB2 and TiN below 1000°C; second step, the solid–liquid solution precipitation reaction in the Fe–Ti–B–N system, resulting in most of TiB2 and TiN reinforcement formation at ∼1100°C. The microstructure investigation reveals that utrafine TiB2 and TiN reinforcements with a size of ∼1 μm are homogeneously distributed in the Fe matrix.

Preparation and scratch test of AlMgB14 modified by TiB2

In this paper, the AlMgB14 and AlMgB14–TiB2 composites were synthesized by means of mechanical alloying and the field-activated and pressure-assisted synthesis process. The effect of temperature and pressure on the purity and property of products was discussed. The results show that the process of preparing AlMgB14 bulk materials is optimized as follows: synthesis temperature 1,400–1,500 °C, heating rate 100 °C·min−1, axial pressure 60 MPa, heat preservation 8–10 min, optimum starting powders’ ratio Al: Mg: B = 0.1915:0.1363:0.6722, and adding excessive 3 wt% Al. The abrasion resistance of AlMgB14 composites with varying amounts of TiB2 was studied using single-point diamond scratch tests with loads ranging from 10 to 100 N in 10 N increments. The scratch width increases almost linearly with the applied load and decreases with TiB2 proportion increasing up to 70 wt%. With its advantages of fast heating, short reaction time, energy conservation, and high purity, this method offers a new way to synthesize AlMgB14 and AlMgB14–TiB2 composites.

Grain refining efficiency and mechanism of pure nickel

According to the selection principle of grain refiners and calculation of planar disregistries, CeO2 and TiB2 particles were selected as the grain refiners of pure nickel. The change of grain size and refining effects of different refiners under the same melting conditions were investigated. The results show that the grain size of pure nickel gradually reduces with increasing the amount of grain refiners. And with increasing the amount of CeO2 up to 0.7 wt%, the grain size of pure nickel decreases from 323.0 to 53.5 μm. In addition, when the amount of TiB2 is 0.7 wt%, the grain size is reduced to 41.3 μm.

FABRICATION OF IN SITUFe-Ti-B COMPOSITE COATING BY LASER CLADDING

Laser cladding was applied to deposit in situ Fe - Ti - B composite coatings on mild carbon steel with precursor of ferrotitanium, ferroboron and pure Fe alloy powders. The composite coatings were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and electron probe microanalysis (EPMA). Wear resistance of the laser-cladded Fe - Ti - B coatings was evaluated under dry sliding condition at room temperature using block-on-ring wear tester. Results indicate that in situ reinforcements of TiB 2 and Fe 2 B can be synthesized in the Fe - Ti - B coatings. The amount of TiB 2 increases with the increase of content of ferrotitanium and ferroboron in the precursor. Reinforcements are formed through the liquid-precipitation route following the solidification path of the Fe - Ti - B system. Hardness and wear properties of the coatings improved significantly in comparison to the as-received substrate due to the presence of hard reinforcements.

Fabrication of in situ TiB2–TiC reinforced steel matrix composites by spark plasma sintering

In situ TiB2 and TiC particulates reinforced steel matrix composites have been fabricated using cheap ferrotitanium and boron carbide powders by spark plasma sintering (SPS) technique. The sintering behaviour and the formation mechanism of the composite were studied. The results show that when the composite was sintered at 1050°C for 5 min, the maximum relative density and hardness of the composite are 99·2% and 83·8 HRA respectively. The phase evolution of the composite during sintering indicates that the TiB2 and TiC reinforcements were formed in situ as follows: first, the solid/solid interface reaction between Fe2Ti and B4C, resulting in the formation of a small amount of TiB2 and TiC below 950°C; second, the solid–liquid solution precipitation reaction in the Fe–Ti–B–C system, resulting in the formation of the main TiB2 and TiC reinforcements at ∼1000°C.