Titanium-based Composites Research Articles

Ultrahigh strength – ductility in Ti–6Al–4V composites with high-activity graphene-induced in-situ TiC and coherent nanophases

Achieving ultra-high strength and ductility of titanium alloys possesses great potential for structural applications in the aerospace and military, yet there is a great challenge for breaking the trade-off barrier of these two properties. In this study, large elongation of ∼10 % and ultra-high tensile strengths of 1510 MPa were obtained in a titanium-based composite. We designed this superior composite based on nanoscale coherent αʹʹ precipitation within near-equiaxed β-Ti as well as micro-scale TiC network architectures along grain boundaries. These in-situ formed triangular αʹʹ coherent precipitates and TiC mainly contributed to the strengthening, while the extremely large elongation resulted from coherent β/αʹʹ interfaces and strain-induced coherent αʹʹ nanotwins. We demonstrated that this composite was easily fabricated using a simple powder metallurgy followed by a hot rolling process. This work can contribute to the design of duplex titanium-based composites as well as other structural materials with exceptional mechanical properties for broad applications.

Laser Additive Manufacturing of Three-Dimensional Ti/TiN Nanotube Arrays with Hierarchical Pore Structures and Promoted Supercapacitor Performances.

Titanium-based composites hold great promise in versatile functional application fields, including supercapacitors. However, conventional subtractive methods for preparing complex-shaped titanium-based composites generally suffer from several significant shortcomings, including low efficiency, strictly simple geometry, low specific surface area, and poor electrochemical performance of the products. Herein, three-dimensional composites of Ti/TiN nanotube arrays with hierarchically porous structures were prepared using the additive manufacturing method of selective laser melting combined with anodic oxidation and nitridation. The resultant Ti/TiN nanotube array composites exhibit good electrical conductivity, ultrahigh specific surface areas, and outstanding supercapacitor performances featuring the unique combination of a large specific capacitance of 134.4 mF/cm2 and a high power density of 4.1 mW/cm2, which was remarkably superior to that of their counterparts. This work is anticipated to provide new insights into the facile and efficient preparation of high-performance structural and functional devices with arbitrarily complex geometries and good overall performances.

Development of Determination Methodology of Electrical Conductivity of Titanium-based Composites

The Ti-based metal matrix composite samples are novel, fabricated by using high voltage electric discharge and spark plasma sintering processes. They have potential usage in the aviation industry. A research that allowed measuring an electrical conductivity of Ti-based composites was performed. A collinear four-point probe method was chosen for measurement of electrical conductivity. Needle-like probes were used to contact the tested sample. Other aspects of the measurement setup are discussed and selected according to relevant literature. A simulation was performed using COMSOL software to validate the measurement method. Furthermore, a simulation performed for contact force of the probes was performed. A 3D model of the measurement tool was created and designed. The measurement setup was tested and validated by using a copper sample. electrical resistance of Ti-based composite samples was measured, and electrical conductivity was calculated. Furthermore, samples were measured at different temperatures and resistivity dependence to temperature was presented. Experimental results are compared to similar research results.

Effect of multi-layer graphene on microstructure and mechanical properties of titanium-based composites

To achieve the enhanced mechanical properties of the titanium grade 5 (Ti64) alloy, multi-layer graphene (MLG) reinforced Ti64 nanocomposites were successfully fabricated by using spark plasma sintering process. Spherical Ti64 particles with an average diameter of 25 μm, MLG with an average diameter of 5 μm, and an average thickness of 2.5 nm were used in the present study. Microstructure study reveals the in-suit reaction between Ti (matrix) and C (reinforcement) that leads to the formation of TiC along the interface. Further, it was observed that a maximum grain refinement of 32.56% occurs in the Ti64/1.2 wt% MLG nanocomposite. Strengthening along the Ti64 and MLG interface and grain refinement are the primary reasons for the enhanced mechanical properties of the nanocomposites. Nanocomposites with 1.2 wt% MLG exhibit nanohardness of 5.29 GPa, elastic modulus of 119.8 GPa which is 68.4% and 140.5% higher compared with that of Ti64 sintered alloy. The results showed that MLG reinforcement plays an important role in improving the mechanical properties of Ti64 nanocomposites.

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

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

Synthesis of Titanium-Based Composites by Pulsed Methods

Ti-based composites with advanced properties were fabricated by the explosion of the wires and magnetic-pulsed compaction methods. After the wire explosion the “metal core – oxide (or nitride) shell” structure is formed. Magnetic-pulsed treatment of such poorly conductive powder leads to the destruction of the shells and to the appearance of an electrical conductivity. This conductivity is only 4-7 times higher than that of pure titanium. As a result of the dynamic compaction of 100-150 nm powder the hot-pressed Ti+9TiO2 composition appeared to have the best combination of mechanical properties: relative density – 95 %, microhardness - 4.2 GPa, reduced modulus of elasticity – 143 GPa, creep under constant load – 105 nm. The coefficients of thermal extension of three materials with different titanium oxide content: 6, 9 and 15 wt. % were measured. The nitride-containing composites were ~30% more porous and had low mechanical properties compared to Ti+TiO2 compacts.

Preparation and Mechanical Properties of Ceramic Fiber Reinforced Titanium-Based Hybrid Laminated Composite

Based on traditional titanium-based composites and the design concept of biomimetic laminated structures, the continuous SiC ceramic fiber, ductile metal Ti foil, and intermetallic Ti2AlNb foil were selected as structural components, which were alternately stacked in the sequence of Ti2AlNb-Ti-SiCf-Ti-Ti2AlNb to prepare the continuous SiC ceramic fiber-reinforced titanium-based laminated composite. The methods adopted were vacuum hot-pressing and ceramic fiber braiding. In the prepared state, the composite’s structural components were metallurgically bonded ideally, and the continuous SiC ceramic fiber was equidistantly distributed in the ductile metal Ti matrix. This composite’s phase is mainly composed of α-Ti, β-Ti, SiC, TiC, O, and B2 phases. In addition, along the ceramic SiC fiber lengthwise, the tensile test was performed on this composite at room temperature and a high temperature of 600°C, with the ultimate tensile strength being 948.76 MPa and 526.62 MPa, respectively, and, in this process, the fiber was debonded and pulled out. Meanwhile, the composite’s bending strength was measured to be 1506.21 MPa in a three-point bending test, and, under this bending load, the mode of crack propagation and failure mechanism were analyzed.

Nearly dense Ti–6Al–4V/TiB composites manufactured via hydrogen assisted BEPM

Titanium matrix composites reinforced with in situ formed titanium boride whiskers have long aroused significant interest for advanced applications in fields such as aerospace, biomedicine, and armaments. However, processing approaches dedicated to fabricating these composites have usually been limited by the cost-performance dilemma, thereby limiting commercial success. Blended elemental powder metallurgy (BEPM) has historically been the most economical route to produce titanium-based composites. At the same time, the need to reduce undue sinter porosities has imposed complicated and expensive extra thermomechanical steps in BEPM manufacturing. In the present study, nearly dense Ti–6Al–4V-based composites reinforced with in situ synthesized titanium monoborides (TiB) are prepared by simple press-and-sinter hydrogen-assisted BEPM without hot deformation or hot pressing using TiH2, TiB2, and master alloy (Al–V) powder blends as starting material. Vacuum sintering of compacted powder blends results in the formation of a dehydrogenated Ti–6Al–4V matrix with excessive porosity and unevenly distributed partially reacted TiB2 particles. Such an inappropriate pre-sintered microstructure can be completely transformed into low-porosity uniform Ti–6Al–4V/TiB composites with tailored grains by using hydrogenation and milling of pre-sintered material into hydrogenated pre-alloyed powders and, finally, by using these powders in a second press-and-sinter processing step. The useful influence of hydrogen as a temporary alloying element on microstructure formation is discussed. The densification of hydrogenated powder compacts upon vacuum heating, and the hydrogen emission from the material is studied via dilatometric tests. The evolution of microstructure and phase composition during processing steps was investigated by scanning electron microscopy and x-ray diffraction. Compressive tests were used to evaluate the mechanical properties of materials produced after the first and second sintering. The results show that hydrogen-assisted BEPM can be a cost-effective route for in situ fabrication of Ti–6Al–4V/TiB composites with reliable mechanical properties.

Synergetic enhancement of strength and ductility for titanium-based composites reinforced with nickel metallized multi-walled carbon nanotubes

Poor ductility of titanium matrix composites with medium/high-strength reinforced with carbonaceous nanomaterials (eg., graphene, carbon nanotubes etc.), has seriously restricted their wide-range engineering and practical industry utility. Herein, we propose a new methodology to significantly and simultaneously enhance both ductility and tensile strength of the titanium matrix composites. We ball milled Ti–6Al–4V (TC4) powders with in-situ chemically synthetized Ni decorated multi-walled carbon nanotubes (i.e MWCNTs@Ni), and then sintered the composites powders using spark plasma sintering (SPS). We achieved both a significant balanced between superior strength and increased ductility of the composite using the MWCNTs@Ni nanopowders. The enhanced strength in composites is mainly attributed to the interfacial structures for effectively enhanced load transfer capability between MWCNTs@Ni and Ti matrix, e.g., the formation of coherent/semi-coherent interfaces among interfacial phases Ti2Ni, TiC and Ti matrix. Furthermore, we applied the dislocation theory to reveal the toughening mechanisms of MWCNTs@Ni in the MWCNTs@Ni/TC4 composites. This study provides a new methodology of fabricating metal matrix composites (reinforced with carbon based nanomaterial) with both high strength and good ductility.

Influence of Elemental Carbon (EC) Coating Covering nc-(Ti,Mo)C Particles on the Microstructure and Properties of Titanium Matrix Composites Prepared by Reactive Spark Plasma Sintering.

This paper describes the microstructure and properties of titanium-based composites obtained as a result of a reactive spark plasma sintering of a mixture of titanium and nanostructured (Ti,Mo)C-type carbide in a carbon shell. Composites with different ceramic addition mass percentage (10 and 20 wt %) were produced. Effect of content of elemental carbon covering nc-(Ti,Mo)C reinforcing phase particles on the microstructure, mechanical, tribological, and corrosion properties of the titanium-based composites was investigated. The microstructural evolution, mechanical properties, and tribological behavior of the Ti + (Ti,Mo)C/C composites were evaluated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), electron backscatter diffraction analysis (EBSD), X-ray photoelectron spectroscopy (XPS), 3D confocal laser scanning microscopy, nanoindentation, and ball-on-disk wear test. Moreover, corrosion resistance in a 3.5 wt % NaCl solution at RT were also investigated. It was found that the carbon content affected the tested properties. With the increase of carbon content from ca. 3 to 40 wt % in the (Ti,Mo)C/C reinforcing phase, an increase in the Young’s modulus, hardness, and fracture toughness of spark plasma sintered composites was observed. The results of abrasive and corrosive resistance tests were presented and compared with experimental data obtained for cp-Ti and Ti-6Al-4V alloy without the reinforcing phase. Moreover, it was found that an increase in the percentage of carbon increased the resistance to abrasive wear and to electrochemical corrosion of composites, measured by the relatively lower values of the friction coefficient and volume of wear and higher values of resistance polarization. This resistance results from the fact that a stable of TiO2 layer doped with MoO3 is formed on the surface of the composites. The results of experimental studies on the composites were compared with those obtained for cp-Ti and Ti-6Al-4V alloy without the reinforcing phase.

Investigating the effect of carbon interfacial layer on the elastoplastic response of ceramic particle-reinforced metal matrix composites

Titanium-based composites with their desirable and great mechanical properties are in high demand. One of the main problems that arise in this field is the chemical reactions that appear between strengthening the material and the matrix that usually undermines the integrity of the composite. This problem will result in dangerous defects such as debonding or degradation of the properties. In this work, a coating solution is presented; a similar process as discussed in the literature yet analytically different. The coating is commonly used for protecting and preserving the reinforcing material’s surface which is in contact with the matrix. Herein, a titanium metal matrix composite reinforced with carbon-coated SiC particles is discussed. Mori-Tanaka method was utilized to firstly determine the properties of the inclusion which is the carbon-coated SiC particle and then using the results based on the thickness of the coating and volume fraction of inclusions, calculating the overall properties of the composite. An incremental method was employed to then calculate the stress-strain curve of the said material. The results obtained were in good agreement with the experimental data. The negative effect of the carbon coating on the elastic properties of the SiC/titanium composite was observed as the coating layer thickness increased. The same thing was observed in the stress-strain curve in the slope of the elastic zone and work hardening growth in the plastic zone.

Fabrication and mechanical properties of dual-heterogeneous titanium-based composites

Abstract Dual-heterogeneous titanium-based composites were designed to maximize the contributions of compositional gradient and multi-layered hetero-structures for strength-ductility synergy. The influences of heterogeneous degree and deformation temperatures on the mechanical properties were evaluated. The underlying mechanism was elucidated from the perspective of temperature-dependent disorder-to-order transition of dislocation configurations.

Composite and Surface Functionalization of Ultrafine-Grained Ti23Zr25Nb Alloy for Medical Applications.

In this study, the ultrafine-grained Ti23Zr25Nb-based composites with 45S5 Bioglass and Ag, Cu, or Zn additions were produced by application of the mechanical alloying technique. Additionally, the base Ti23Zr25Nb alloy was electrochemically modified in the two stages of processing: electrochemical etching in the solution of H3PO4 and HF followed by electrochemical deposition in Ca(NO3)2, (NH4)2HPO4, and HCl. The in vitro cytocompatibility studies were also done with comparison to the commercially pure titanium. The established cell lines of Normal Human Osteoblasts (NHost, CC-2538) and Human Periodontal Ligament Fibroblasts (HPdLF, CC-7049) were used. The culture was conducted among the tested materials. Ultrafine-grained titanium-based composites modified with 45S5 Bioglass and Ag, Cu, or Zn metals have higher biocompatibility than the reference material in the form of a microcrystalline Ti. Proliferation activity was at a stable level with contact with studied materials. In vitro evaluation research showed that the ultrafine-grained Ti23Zr25Nb-based composites with 45S5 Bioglass and Ag, Cu, or Zn additions, with a Young modulus below 50 GPa, can be further used in the biomedical field.

Microstructure and mechanical properties of iron-containing titanium metal-metal composites

Titanium-based metal-metal composites show promises in many applications. In this work, iron-containing titanium-based composites were fabricated by using powder metallurgy method and rotary swaging process. Titanium-based composites with steel addition were sintered at temperature below TiFe eutectic temperature. Increase of the steel addition to 23% resulted in formation of TiFe intermetallic and density decrease in the composites. Further, the as-sintered composites present relatively good workability so hot rotary swaging of the as-sintered composites can be conducted. Steel particles were diffused into the Ti matrix and the composite transformed to a discontinuous β-Ti fiber-reinforced structure. As a result, mechanical properties (in axial direction) of the swaged composites were significantly improved. The tensile strength and elongation reached 1360 MPa and 9.3%, respectively.

Additive manufacturing of low-cost porous titanium-based composites for biomedical applications: Advantages, challenges and opinion for future development

Titanium and its alloys have received considerable attention for biomedical applications such as orthopaedic implants due to their outstanding mechanical properties and excellent biocompatibility. However, their composition, structural design and fabrication can be further tailored to improve key properties to make them more compatible with the human body and reduce their expense so that they can better compete with conventional metallic biomaterials. In this work, we provide a concise overview of additive manufacturing technologies and their application to biomedical titanium-based materials with a focus on the main achievements and issues which remain to be addressed. Subsequently, we highlight the potential to develop additive manufacturing of novel, low-cost porous titanium composites to meet the needs for biomedical orthopaedic implants. The article provides a pathway to their development through the application of alloy composition design and reinforcement strategies, manufacturing optimisation and identification of process-structure-property relationships controlling performance in combination with computer-aided structural design tools. This work aims to provide a platform for cost-effective manufacture of titanium composite orthopaedic implants with enhanced lifespans and structural compatibility.

Unlocking the metastable phases and mechanisms in the dehydrogenation process of titanium hydride

There are many advantages of using titanium hydride (TiH2) as a starting material for the fabrication of titanium products. However, a thorough understanding of the dehydrogenation process in the fabrication is crucial to ensure the high quality of the Ti components to be produced. In this work the phase transformations sequence during the dehydrogenation of TiH2 powder to titanium have been investigated in detail using thermal analysis, high temperature XRD and Rietveld refinement. With the application of Rietveld refinement, the cell parameters and phase changes have been accurately determined, and the results reveal that the dehydrogenation of TiH2 to Ti consists of several steps and involves a few previously unreported metastable phases and the equilibrium phases. The metastable phases actually possess the same crystal structures as those of the equilibrium phases, but with different lattice parameters. Under some conditions the metastable phases will be retained at ambient temperature. These metastable phases have been confirmed by transmission electron microscopy (TEM) and selected area electron diffraction (SAED). A step-transition mechanism has been proposed to explain the transformation process. This study will be useful for the fabrication of titanium-based composites and titanium alloys from TiH2 powder.

Synthesis and Characterization of Complex Nanostructured Thin Films Based on Titanium for Industrial Applications.

Titanium-based composites—titanium and silver (TiAg) and titanium and carbon (TiC)—were synthesized by the Thermionic Vacuum Arc (TVA) method on substrates especially for gear wheels and camshaft coating as mechanical components of irrigation pumps. The films were characterized by surface morphology, microstructure, and roughness through X-ray Diffraction (XRD), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Small-Angle Neutron Scattering (SANS). The silver (Ag) films crystallized into a cubic system with lattice a = 4.0833 Å at room temperature, indexed as cubic Ag group Fm3m. The crystallites were oriented in the [111] direction, and mean grain size was <D>111 = 265 Å. The TiC structure revealed a predominant cubic TiC phase, with a = 0.4098 as a lattice parameter determined by Cohen’s method. Average roughness (Ra) was 8 nm for the as-grown 170 nm thick TiAg film, and 1.8 nm for the as-grown 120 nm thick TiC film. Characteristic SANS contribution was detected from the TiAg layer deposited on a substrate of high-quality stainless steel with 0.45% carbon (OLC45) in the range of 0.015 Å−1 ≤ Q ≤ 0.4 Å−1, revealing the presence of sharp surfaces and an averaged triaxial ellipsoidal core-shell object.

Improved cathodic oxygen reduction and bioelectricity generation of electrochemical reactor based on reduced graphene oxide decorated with titanium-based composites

A kind of reduced graphene oxide decorated with titanium-based (RGO/TiO2) composites are successfully synthesized and employed in this current study as a novel nonprecious metal catalyst for enhancing bioelectricity generation and cathodic oxygen reduction reaction (ORR) in single chamber microbial fuel cells (MFCs). Compared with commercial Pt/C, RGO/TiO2 shows obviously enhanced oxygen reduction reaction activity due to the appropriately-permeated, large electrochemical active area, enough exposure of electrocatalytic active sites of RGO/TiO2. The air-cathode MFC with RGO/TiO2-1 cathode achieves 1786.7 mW m−3 of power density, 86.7% ± 1.2% of COD removal and 31.6% ± 1.1% of CE, which are higher than commercial Pt/C. Moreover, RGO/TiO2-1 cathode exhibits high-effective electrocatalytic activity, and the power density of RGO/TiO2-1 can keep a stable level and only has a minor decline (5.35%) during 30-cycles operation. These results indicate that RGO/TiO2-1 is a potential cathode catalyst, markedly enhancing cathode ORR, wastewater treatment efficiency, and bioelectricity generation of MFC.

Oxygen-Induced Mechanical Property Variations of Rapidly Solidified Ti-Based Bulk Metallic Composites

In titanium-based metallic glass composites, a new kind of structural material, the presence of oxygen is an unavoidable problem. Since the amorphous matrix is very sensitive to oxygen, oxygen content must be carefully controlled during the manufacturing process. In this paper, the effects of oxygen on the microstructure and mechanical properties of Ti48Zr20Nb12Cu5Be15 metallic glass composite was studied. The results showed that even low concentrations of oxygen in the metallic glass composite are sufficient to significantly affect the strength, plasticity and working hardening ability without altering the microstructure of the composite on micron scale. Acceptable oxygen content ranges in Ti48Zr20Nb12Cu5Be15 metallic glass composites for practical applications can be determined by balancing the stability of the amorphous matrix and the strength and plasticity of the alloy.

Fabrication of Hybrid Materials from Titanium Dioxide and Natural Phenols for Efficient Radical Scavenging against Oxidative Stress.

Oxidative stress caused by free radicals is one of the great threats to inflict intracellular damage. Here, we report a convenient approach to the synthesis, characterization, and evaluation of the radical activity of titanium-based composites. We have investigated the potential of natural antioxidants (curcumin, quercetin, catechin, and vitamin E) as radical scavengers and stabilizers. The titanium oxide composites were prepared via three steps including sol-gel synthesis, carboxylation, and esterification. The characterization of the titanium-phenol composites was carried out by FTIR, PXRD, UV-vis and SEM methods. The radical scavenging ability of the novel materials was evaluated using DPPH and an in vitro LPO assay using isolated rat liver mitochondria. The novel materials exhibit both a higher stability and an antioxidant activity in comparison to bare TiO2. It was found that curcumin and quercetin based composites show the highest antioxidant efficiency among the composites under study followed by catechin and vitamin E based materials. The results from an MTT assay carried out on the Caco-2 cell line indicate that the composites do not contribute to the cytotoxicity in vitro. This study demonstrates that a combination of powerful antioxidants with titanium dioxide can change its functional properties and provide a convenient strategy against oxidative stress.