Ti-TiB Composites Research Articles

Effect of hot-pressing sintering temperature and pressure on the densification and properties of Ti-TiB composites

Ti/TiB composites exhibit promising potential for applications in the automotive, aerospace, and biomedical sectors. Hot pressing coupled with in situ reaction synthesis is a commonly employed technique for fabricating discontinuously TiB-reinforced titanium matrix composites. Despite its efficacy, comprehensive research investigating the influence of hot-pressing process parameters on the densification and properties of these composites remains scarce. This study systematically examined the effects of pressure (16–48 MPa) and temperature (1250 °C to 1350 °C) on the density, microstructure, and mechanical properties of Ti/TiB composites produced through hot pressing. By analyzing densification curves and rate curves, the densification behavior under varying processing conditions was elucidated. The results indicate that elevated sintering temperatures and pressures correlate with increased densification rates, reduced porosity, and enhanced sample density. A strong relationship between relative densities and hardness was observed. This research contributes to a deeper understanding of the hot-pressing sintering process for Ti-TiB composites and facilitates the optimization of processing conditions.

Fatigue Crack Growth Behavior of Additively Manufactured Ti Metal Matrix Composite with TiB Particles

Fatigue crack growth behavior of additively manufactured Ti metal matrix composite with TiB particles at room temperature was studied using a compact tension specimen and at the stress ratio of 0.1 (R = 0.1). The composite studied in this work was manufactured with a unique additive technique called plasma transferred arc solid free-form fabrication, which was designed to manufacture low-cost near-net-shaped components for aerospace and automotive industries. The fatigue crack growth rate experiments were carried perpendicular and parallel to the additive material build, aiming to find any fatigue anisotropies at room temperature. The findings reveal that additively manufactured Ti-TiB composite shows isotropic fatigue properties with respect to fatigue crack growth. Furthermore, the fatigue crack growth mechanisms in this additive composite material were identified as void nucleation/coalescence and the bypassing of particles and matrix, depending on the interparticle distance.

Refined microstructure and enhanced wear resistance of titanium matrix composites produced by selective laser melting

In order to investigate the effect of TiB2 contents on the microstructure and wear resistance of titanium matrix composites, commercial pure Ti (CP-Ti) powders with 0–7.5 wt.% TiB2 particles were melted by selective laser melting (SLM) to produce the in-situ Ti-TiB composites. When the TiB2 content increases from 2.5 wt.% to 7.5 wt.%, the microstructures of the Ti-TiB composites undergo a transition from the single phase of α′-Ti to the mixed phases of α′-Ti, TiB and TiB2, and the acicular α′-Ti is refined significantly from 1.03 ± 0.24 μm to 0.36 ± 0.05 μm, showing that increasing the TiB2 content induces the formation of TiB and refines the microstructure. Moreover, large TiB2 particles are not melted completely and they react with the Ti matrix liquid to form a TiB layer around the Ti matrix during SLM. However, small TiB2 particles are completely dissolved into the Ti matrix liquid so that the eutectic TiB grains are precipitated at the boundaries of the Ti matrix after in-situ reaction of TiB2 with Ti. The formation of α′ martensite in the titanium matrix and the addition of TiB2 can induce the fine grain strengthening, the dispersion strengthening, the solid solution strengthening in the SLM-produced composites. The results indicate that the microhardness of the composites increases from 258 ± 10.3 HV0.2 to 435 ± 14.7 HV0.2. The wear process of the SLM-produced CP-Ti and TiB2 reinforced Ti matrix composites is accompanied by adhesion wear, abrasive wear and oxidation wear. As a result, when the TiB2 content increases to 7.5%, the wear resistance of the composites increases by 32.6% compared with that of the CP-Ti. These improvements are mainly due to strengthening and hardening effects induced by TiB2 particles and refinement of Ti matrix. This study provides some basis for developing wear-resistant and high-strength titanium alloys.

3D ink-extrusion printing and sintering of Ti, Ti-TiB and Ti-TiC microlattices

Titanium metal matrix composite microlattices are fabricated using 3D ink extrusion printing and sintering. The inks consist of TiH2+TiB2 or TiH2+TiC powder blends to form (i) Ti-TiB composites by dehydrogenation and in situ reaction of Ti + TiB2 to form Ti + TiB and (ii) Ti-TiC composites, where TiC remains stable during the sintering process. Rapid densification of the printed powder blend is achieved during pressureless sintering in vacuum at 1200 °C between 1 and 4 h, due to the small Ti particle size available from dehydrogenation of micron-sized TiH2. Near-full density Ti-TiB and Ti-TiC is achieved within individual lattice struts, despite high TiB and TiC volume fractions up to 25 vol.%. The added TiB2 particles are fully dissolved and re-precipitated to TiB whiskers and whisker clusters in <0.5 h. The compressive properties of sintered cross-ply microlattices are measured for the three types of composites (Ti-TiB, Ti-TiC and Ti-TiC(W), with W originating from powder contamination) and pure Ti controls as a function of lattice orientation with respect to load. The compressive strength of the Ti-TiB/TiC composites increases from 55 to 1019 MPa as the designed lattice macroporosity is reduced from 71 to 24 %, and scales with the third power of relative density, indicating a high sensitivity of strength with relative density.

Effect of Titanium Diboride Content on Basic Mechanical Properties of Composites Sintered from TiH2 + TiB2 Powder Mixtures

The paper examines how the titanium diboride content of the starting TiH2–TiB2 powder mixture influences basic mechanical properties of the resultant sintered composites in tension and compression tests. The porosity of the compacts sintered at 1250°C increases with greater titanium diboride content of the starting mixture, which is associated with the Frenkel effect that occurs in the sintering process. Although the porosity somewhat increases, the strength, hardness, and elastic modulus in tension become higher when 5% TiB2 powder is introduced into the charge. These characteristics however decrease when the high-modulus component increases to 10% in the charge. The ductility of the sintered alloys monotonically reduces with higher boride content. The yield point and compressive strength monotonically increase with higher TiB2 content of the charge, despite greater porosity. This occurs because porosity has a significantly weaker effect on the strain resistance of the sintered Ti–TiB composites in compression than in tension.

Cost-affordable, high-performance Ti–TiB composite for selective laser melting additive manufacturing

Abstract

Effect of TiB2 content on microstructure and properties of in situ Ti-TiB composites

This study determined the optimal concentration of titanium diboride (TiB2) particles for the development of in situ titanium–titanium boride (Ti–TiB) metal matrix composites (MMCs) prepared by a conventional powder metallurgy route to be used for industrial applications. The effect of concentration of TiB2 particles was studied by reinforcing TiB2 powder in different mass fractions (2wt%, 5wt%, 10wt%, and 20wt%) into pure Ti powder during the fabrication process. The MMCs were sintered at high temperatures under vacuum. The transmission electron microscopy (TEM) results revealed the formation of needle-shaped TiB whiskers, indicating that in situ reaction occurred during vacuum sintering of the powder compacts. All the composite samples had a high sintered density, and the hardness of the composites increased with an increase in the mass fraction of reinforcement. Mechanical and tribological properties such as flexural strength, impact, and wear properties were determined and found to be dependent on the mass fraction of the reinforcement. However, the mechanism for the in situ reaction needs further investigation by high-energy in situ X-ray diffraction techniques.

In situ neutron diffraction observations of Ti-TiB composites

This paper characterizes and evaluates TiB/Ti composites during thermal treatment using in situ neutron diffraction. The composites were developed using a conventional press and sinter technique. Pure titanium (Ti) was chosen as the matrix, and different concentrations of TiB2 were used as the boron source for the in situ development of the TiB phase. The conversion of phases from TiB2 (2–10 wt.%) to TiB during heating and cooling in the Ti matrix was studied for the first time using in situ neutron diffraction. No metastable phases were observed during heat-treating of the samples. Microstructural evolution and tensile properties of these composites were also evaluated with the highest tensile strength recorded of 684.95 MPa for the sample containing 5 wt.% TiB2.

Effect of TiB2 addition on the elevated temperature tribological behavior of spark plasma sintered Ti matrix composite

The study aims at the investigation of the high temperature tribological behavior for in situ synthesized Ti–TiB composite and reports thorough characterization of worn surfaces to understand the operative wear mechanisms to clarify the controversial role of tribo-oxide formation in Ti alloys. Therefore monolithic CpTi and CpTi+9.6 wt% TiB2 composite specimens were fabricated by spark plasma sintering. Microstructural and phase analyses verified the in situ formation of TiB whiskers in the composite specimens and an enhancement in hardness. The dry sliding wear behavior of composites was better than CpTi, across all testing temperatures, thanks to better hardness and the formation of adherent and thicker tribo-oxide layer.

Tensile Fracture of TiB Whisker Reinforced Ti Alloy Matrix Composites

TiB whisker reinforced Ti alloy matrix (Ti–TiB) composites have attracted attention as the aerospace materials with their high specific mechanical properties for long time. However, strengthening mechanism of Ti–TiB composites has not been revealed because of the agglomeration and incomplete precipitation of TiB whiskers in the Ti alloy matrix yet. In this study, we addressed to fabricate fully-dense TiB whisker reinforced Ti-6Al-4V alloy matrix (Ti6Al4V–TiB) composites via powder metallurgical process, which have the microstructure to discuss their tensile properties with the theories for composite materials. The Young’s modulus and ultimate tensile strength of Ti6Al4V–10 vol% TiB composite were 130 GPa and 1193 MPa, respectively. Note that the elongation of Ti6Al4V–10 vol% TiB composite was approximately 2.8 % although the elongations of Ti–TiB composite have been reported are few (; less than 1%) due to the agglomeration of TiB whiskers in Ti matrix.

On the physical and mechanical properties of spark plasma sintered pure Ti and Ti-TiB composite

The physical and mechanical properties of spark plasma sintered pure Ti and Ti-TiB2 composite were investigated as a function of TiB2 concentration and sintering temperature. Experiments were conducted using the response surface methodology based on a full factorial design in order to model and evaluate the responses, namely sintered density, porosity, ultimate tensile strength, elongation, bending strength and micro-hardness. Analysis of variance was performed to evaluate the acceptability of the developed models. In order to confirm the accuracy of developed models, results of analyses by x-ray diffraction, optical and scanning electron microscopy from polished and fracture surfaces were investigated, in details. It was concluded that the sintering temperature has the most pronounced effect on the sintered density, porosity, and micro-hardness, while the TiB2 has the most pronounced effect on the ultimate tensile strength, elongation, and bending strength. Results showed that by introducing of TiB2 the strengthening occurs through grain refinement of matrix and in-situ formation of TiB needle like phases. Finally, it is concluded that the predicted values of responses obtained using mathematical models were in good agreement with the microstructural characteristics of sintered samples and optimum conditions for getting desired properties obtained using purposed models.

Microstructure Characterization of &lt;i&gt;In Situ&lt;/i&gt; Ti-TiB Metal Matrix Composites Prepared by Powder Metallurgy Process

Metal matrix composites (MMCs) are the new generation materials that combine both the metallic properties (ductility and toughness) and ceramic characteristics (high strength and modulus), leading to higher strength in shear and compression, at higher service temperatures. Titanium matrix composites possess light weight, high strength and good corrosion resistance and are used as structural materials in automobiles and aerospace industries. In the present study, in situ Ti-TiB composites were fabricated by reinforcing (2, 5, 10 and 20 wt. %) TiB2 powder (mean size &lt;10 microns) into titanium powder (mean particle size ~26.58 μm) and subsequently consolidated by vacuum sintering at 1300 °C for 3 h. X-ray diffraction, scanning electron microscopy (SEM) and density measurements were carried out to characterize the prepared composites. The results showed that all compositions led to high density composites, and the hardness of the composites increased with an increase in the amount of reinforcement. The mechanism of vacuum sintering is yet to be understood in the consolidation of composites and the detailed evolution of microstructure needs to be analysed.

Role of powder metallurgical processing and TiB reinforcement on mechanical response of Ti–TiB composites

In this work, titanium–titanium boride (Ti–TiB) composites were synthesized by three different powder metallurgical techniques, namely, spark plasma sintering (SPS), hot iso-static pressing (HIP) and vacuum sintering (VS). The mechanical properties of the composites were determined using the nanoindentation technique. The role of the material processing route and TiB reinforcement employed on the mechanical properties of the composites was investigated. The results revealed that the composites processed by SPS possessed improved mechanical properties relative to those of the composites prepared by the HIP and VS techniques. Furthermore, reinforcement of the composites with TiB enhanced the hardness, elastic modulus and contact stiffness, whereas it reduced the fracture toughness and indentation creep.

Mechanical behavior of porous commercially pure Ti and Ti–TiB composite materials manufactured by selective laser melting

Commercially pure titanium (CP-Ti) and Ti–TiB composite parts with three different porosity levels (i.e. 10%, 17% and 37%) were produced by selective laser melting (SLM). Scanning electron microscopy (SEM) investigations show that martensitic (α′) microstructure exists in SLM-processed CP-Ti parts, whilst SLM-processed Ti–TiB composites present needle-shape TiB particles distributed in α-Ti matrix. Mechanical properties of these porous samples decrease with porosity level increasing. The yield strength and elastic modulus of porous CP-Ti parts range 113–350MPa and 13–68GPa respectively, which are much lower than those for porous Ti–TiB counterparts (234–767MPa and 25–84GPa respectively) mainly due to the strengthening effect induced by TiB particles in Ti–TiB samples. Compression stress–strain curves of 37% porous CP-Ti parts show a typical three-stage behavior of ductile porous metals. Also, the elastic moduli of both 37% porous CP-Ti and Ti–TiB samples are similar to that of human bone. SEM investigations of the porous CP-Ti samples after compression testing show that no crack presents until 50% compressive strain and most of deformation is absorbed by porous areas. In contrast, μ-CT investigations indicate that all porous Ti–TiB samples fail at early stages of compression testing due to cracks resulting from insufficient ductility of struts of porous areas, because they are not able to accommodate high strains of the deformation at high strengths.

Synthesis and Characterization of Ti-TiB Composites Processed through Vacuum Sintering

In the present work, an attempt has been made to explore the general microstructural characteristics and mechanical properties of titanium-titanium boride (Ti-TiB) composites (20 and 40 vol.% TiB reinforcement in Ti matrix) processed by Vacuum Sintering. The microstructures of the composites were investigated using electron probe micro analysis, scanning electron microscopy and X-ray diffraction. Obviously, the elastic modulus, shear modulus and hardness are found to increase with increase in volume fraction of titanium boride. The effects of titanium boride reinforcements on elastic properties and microhardness are discussed.

Comparative study of microstructures and mechanical properties of in situ Ti–TiB composites produced by selective laser melting, powder metallurgy, and casting technologies

Abstract

Reaction mechanism, microstructure and properties of Ti–TiB insitu composite processed by spark plasma sintering

Conventionally, Ti–TiB composites have been processed using TiB2 or elemental boron in titanium. We report a novel method of processing Ti–TiB composite insitu through reaction between an inexpensive precursor, KBF4, and Ti using spark plasma sintering (SPS). The reaction mechanism was evaluated by differential scanning calorimetry (DSC) in combination with X-ray diffraction (XRD) and scanning electron microscopy (SEM). The reaction happens in steps that involve different intermediate phases which finally lead to TiB. No residual TiB2 was found in the final composite unlike other methods. The insitu formed TiB whiskers refined the grain size and also homogenized the microstructure. The hardness and compressive strength increased significantly compared to cp Ti processed under same conditions.

Numerical Simulation for Residual Stresses of the Spark Plasma Sintered Ti–TiB Composites

Numerical Simulation for Residual Stresses of the Spark Plasma Sintered Ti–TiB Composites

Simulation of the Temperature Distribution of Gradient Ti-TiB Composites Prepared by Spark Plasma Sintering Process

An electrical – thermal coupled finite element model (FEM) is developed to investigate the temperature distribution during spark plasma sintering (SPS) with a pre-designed graded graphite die. The sample used in this investigation consists of five layers with different contents of Ti and TiB (45 wt % Ti, 55 wt %Ti, 65 wt % Ti, 75 wt % Ti and 85 wt % Ti). The temperature distribution in gradient Ti-TiB composites was obtained. Owing to the use of the die with changing cross section, a temperature difference of 142K in the axial direction inside the sample is achieved, while the maximum radial temperature difference is 6.2 times less than the axial one.

Improving Corrosion Resistance of Ti–TiB Composite Using Gas Tungsten Arc Heating

Titanium composites are used for applications requiring a combination of specific strength and corrosion resistance. Titanium–titanium boride (Ti–TiB) composite is gaining importance for some specific applications like armors of military hardware, biomedical applications, and its ease of making through routes like reactive sintering. In this research work, the surface of the Ti–TiB composite has been modified using Gas Tungsten Arc (GTA) heating and was characterized for corrosion resistance. The electrochemical polarization test confirms that corrosion resistance has improved due to surface treatment using gas tungsten arc. The micrographs of scanning electron microscopy (SEM) reveal the mechanism responsible for improvement in corrosion resistance.