Titanium-based Composites Research Articles

A Review of Spark Plasma Sintering of Carbon Nanotubes Reinforced Titanium-Based Nanocomposites: Fabrication, Densification, and Mechanical Properties

The quest to consistently develop improved materials for direct application in automotive, aerospace, and other industries has led to the synthesis of titanium-based composites—with current research efforts being directed toward the utilization of carbon nanotubes (CNTs) as reinforcement. CNTs constitute an outstanding reinforcement for titanium-based matrixes, owing to their extraordinary physical, electrical, mechanical, and thermal properties. Powder metallurgy (PM) routes have been adjudged the most promising technique for synthesizing CNT-reinforced titanium. However, past reviews have highlighted various PM techniques, reinforcement efficiency, and effective methods for dispersing CNTs in metal matrixes. Among the various PM techniques, spark plasma sintering (SPS) has gained popularity in the synthesizing of titanium-based nanocomposites (TMNCs). Hence, this review focused on past works on the SPS of TMNCs reinforced with CNTs. The properties of CNTs, their fabrication method, their densification mechanism, and the mechanical properties of sintered TMNCs were discussed in detail.

Titanium Alloys 2017

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Bioactivity of novel functionally structured titanium-ceramic composites in contact with human osteoblasts.

The aim of this study was to analyze the osteogenic cell behavior on the surface of novel functionally graded titanium-based composites containing bioactive ceramics. Titanium grade V discs (8 × 3 mm) embedding gradual content of hydroxyapatite (TiAlV-HA) or beta-tricalcium phosphate (TiAlV-βTCP) were produced by hot-pressing technique. Titanium-ceramic composite discs and Ti grade V (control group) were placed in contact with human osteoblast culture assays. The morphology and adhesion of osteoblasts were inspected by field emission guns scanning electron microscopy (FEGSEM) while cell viability was assessed by fluorometric method. Alkaline phosphatase (ALP) activity and fluorescent microscopic analyses were used to evaluate mineralization on the test and control discs. FEGSEM images showed cells adhered to Ti6Al4V-ceramic and Ti6Al4V surfaces over a period of 24 h, and therefore, an intense proliferation of osteoblasts and spreading cells was noticed for 7 days. Cell viability increased with time on all the surfaces although TiAlV-βTCP revealed significant higher percentage of cell viability than that recorded for TiAlV-HA (p < 0.01). TiAlV-βTCP also showed the highest hydrophilic character. ALP levels increased on the Ti6Al4V-ceramic surfaces when compared to the control group. Also, a qualitative analysis of mineralization evidenced an increase in mineral content on TiAlV-HA or TiAlV-βTCP groups. Novel functionally graded composites based on Ti grade V and hydroxyapatite or βTCP showed a higher bioactivity in presence of osteoblasts than that recorded on Ti grade V. Also, such functionally graded materials can prevent risks of failures by detachment of bioactive ceramic materials during implant placement. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1923-1931, 2018.

Powder-materials impact on nanoparticle-reinforced Ti-6Al-4V matrix composites produced via inductive hot pressing

This paper addresses the optimal manufacture of titanium alloy composites via inductive hot pressing, and studies the influence of nanosized reinforcement and matrix powders on the final properties of the titanium-based composites. Before hot consolidation, two types of Ti-6Al-4V powders were mixed with various percentages of nano-diamonds. After inductive hot pressing at 900°C and 950°C, characterisation of the specimens took place, which revealed significant differences in the final properties of the composites produced. Further to the well-known effect of how oxygen content in the initial powder considerably affects the properties of the specimens, the influence of the nano-diamonds in the microstructure is also evaluated.

Analysis of the Microstructure and Mechanical Properties of Titanium-Based Composites Reinforced by Secondary Phases and B₄C Particles Produced via Direct Hot Pressing.

In the last decade, titanium metal matrix composites (TMCs) have received considerable attention thanks to their interesting properties as a consequence of the clear interface between the matrix and the reinforcing phases formed. In this work, TMCs with 30 vol % of B4C are consolidated by hot pressing. This technique is a powder metallurgy rapid process. Incorporation of the intermetallic to the matrix, 20 vol % (Ti-Al), is also evaluated. Here, the reinforcing phases formed by the reaction between the titanium matrix and the ceramic particles, as well as the intermetallic addition, promote substantial variations to the microstructure and to the properties of the fabricated composites. The influences of the starting materials and the consolidation temperature (900 °C and 1000 °C) are investigated. By X-ray diffraction, scanning and transmission electron microscopy analysis, the in-situ-formed phases in the matrix and the residual ceramic particles were studied. Furthermore, mechanical properties are studied through tensile and bending tests in addition to other properties, such as Young’s modulus, hardness, and densification of the composites. The results show the significant effect of temperature on the microstructure and on the mechanical properties from the same starting powder. Moreover, the Ti-Al addition causes variation in the interface between the reinforcement and the matrix, thereby affecting the behaviour of the TMCs produced at the same temperature.

Metallic Composites Strengthened with Intermetallic Reinforcing Elements

An efficient method which uses explosion welding to obtain titanium-based composites with isotropic mechanical properties is examined. A new scheme has been devised for strengthening a composite on the basis of preliminary mathematical modeling in the program Cosmos Works. The relationship of the material’s thermal loading regime to its phase composition and volumetric content of reinforcing intermetallic elements is studied.

Comparative in vitro study regarding the biocompatibility of titanium-base composites infiltrated with hydroxyapatite or silicatitanate

BackgroundThe development of novel biomaterials able to control cell activities and direct their fate is warranted for engineering functional bone tissues. Adding bioactive materials can improve new bone formation and better osseointegration. Three types of titanium (Ti) implants were tested for in vitro biocompatibility in this comparative study: Ti6Al7Nb implants with 25% total porosity used as controls, implants infiltrated using a sol–gel method with hydroxyapatite (Ti HA) and silicatitanate (Ti SiO2). The behavior of human osteoblasts was observed in terms of adhesion, cell growth and differentiation.ResultsThe two coating methods have provided different morphological and chemical properties (SEM and EDX analysis). Cell attachment in the first hour was slower on the Ti HA scaffolds when compared to Ti SiO2 and porous uncoated Ti implants. The Alamar blue test and the assessment of total protein content uncovered a peak of metabolic activity at day 8–9 with an advantage for Ti SiO2 implants. Osteoblast differentiation and de novo mineralization, evaluated by osteopontin (OP) expression (ELISA and immnocytochemistry), alkaline phosphatase (ALP) activity, calcium deposition (alizarin red), collagen synthesis (SIRCOL test and immnocytochemical staining) and osteocalcin (OC) expression, highlighted the higher osteoconductive ability of Ti HA implants. Higher soluble collagen levels were found for cells cultured in simple osteogenic differentiation medium on control Ti and Ti SiO2 implants. Osteocalcin (OC), a marker of terminal osteoblastic differentiation, was most strongly expressed in osteoblasts cultivated on Ti SiO2 implants.ConclusionsThe behavior of osteoblasts depends on the type of implant and culture conditions. Ti SiO2 scaffolds sustain osteoblast adhesion and promote differentiation with increased collagen and non-collagenic proteins (OP and OC) production. Ti HA implants have a lower ability to induce cell adhesion and proliferation but an increased capacity to induce early mineralization. Addition of growth factors BMP-2 and TGFβ1 in differentiation medium did not improve the mineralization process. Both types of infiltrates have their advantages and limitations, which can be exploited depending on local conditions of bone lesions that have to be repaired. These limitations can also be offset through methods of functionalization with biomolecules involved in osteogenesis.

Effect of Calcium Titanate and/or Titanium-Phosphides in the Properties of Titanium Composites for Implant Materials

Titanium-based composites containing TixPy phase (s) or CaTiO3 and TixPy phase (s) were produced by a non conventional method using suitable mixtures of TiH2 powder and phosphoric acid (TiH2/P), or TiH2 and 10 vol.% of calcium phosphate (TiH2/CP), respectively. The composites were produced with the same phosphor molar concentration. The mixtures were prepared by ultrasound in water, dried in a rotary evaporator, pressed at 600 MPa and vacuum-sintered at 1200 °C for 2 hours. The mixtures were well dispersed by ultrasound and agglomerate-free. The analyses show that titanium particles were coated with TixPy phase (s) for the TiH2/P composite or with an intermediary layer of TixPy phase (s) and an external deposit of calcium titanate for the TiH2/CP composite. The TiH2/P composite presented higher compressive strength and about the same contact angle compared to the TiH2/CP composite. However, both materials displayed lower contact angle than that of pure titanium.

Processing Effect on the Compressive Strength and Bioactivity of Ti-Based Composites Produced with TiH&lt;sub&gt;2&lt;/sub&gt; and Calcium Phosphate

Titanium-based composites with bioactive phases were produced with TiH2and 10% in volume of calcium phosphate. The mixtures were prepared either by conventional powder metallurgy processing or by ultrasound, dried in a rotary evaporator, pressed at 600 MPa and vacuum-sintered at 1200 °C for 2 hours. Crystal phases of the as-fabricated composites are found to be α-Ti, CaTiO3and TixPyphase (s). The TixPyand CaTiO3phases resulted from the reaction between titanium and tricalcium phosphate at about 1130 °C. Calcium phosphate was better dispersed by ultrasound leading to a higher compressive strength of the composite and a more uniform Ca-P deposition in simulated body fluid solution.

Structure and Mechanical Properties of Titanium-Based Composites and Secondary Films Synthesized during Friction

The structural state and mechanical characteristics of titanium-based composites and secondary lubricating films synthesized on their surface during dry friction are studied. It is found that secondary lubricating films with microheterogeneous and nanocrystalline (grain size <100 nm) structure are synthesized on the materials whose friction coefficient varies between 0.3–0.36 and wear between 1.91–68.3 mg/km at a high slip velocity (15 m/sec) and low pressure (0.8 MPa). These films determine the antifriction properties and performance of the materials. The mechanical characteristics of secondary lubricating films are higher than those of the composites. The antifriction properties can be evaluated from the ratio of the mechanical characteristics of the secondary lubricating films and the starting material: the smaller the ratio, the higher the antifriction properties of the composite.

Grinding Experiments on PTMCs with Vitrified CBN Wheel

Grinding experiments were conducted using vitrified CBN wheel on particulate reinforced titanium-based matrix composites (PTMCs) and Ti-6Al-4V matrix. The issues discussed are grinding forces, surface roughness, and the formation of surface integrity. The main results are summarized as follows: (1) The grinding forces increase with the increasing workpiece speed and depth of cut during grinding PTMCs and Ti-6Al-4V materials. (2) Decreasing depth of cut properly contribute to obtaining finished surface with good surface during grinding of PTMCs using CBN wheel, but the workpiece speed has little influence on the surface roughness value of PTMCs. (3) The formation of surface integrity of PTMCs is due to the combined removal of the TiC and TiB reinforcements and the Ti-6Al-4V matrix.

Static X-Ray Scans on the Titanium Hydride (TiH&lt;sub&gt;2&lt;/sub&gt;) Powder during Dehydrogenation

This work investigates the dehydrogenation of TiH2 powder during isothermal heating at 600°C using the static x-ray scans of high temperature x-ray diffraction (XRD). As-received TiH2 powder with a particle size of 5 μm and purity of 99.1% was used for this measurement. With increasing temperature, phase transformations occurred because of dehydrogenation and it happened very fast. It was found that during the phase transformation of TiH2 to titanium, some transitional phases observed and occurred. This finding confirmed the in-situ determination of TiH2 powder dehydrogenation by using Rietveld Refinement Method from our previous research. This study is useful for the fabrication of titanium-based composites and titanium alloys from TiH2 powder because the different phases in TiH2 will affect the final mechanical properties in titanium.

Prospects of Improving the Tribotechnical Characteristics of Titanium Composites

Titanium-based composites containing MoS2, MoSe2, CaF2, and BN solid lubricants are synthesized. Their tribological characteristics are investigated without lubrication at different sliding velocities (0.5, 1, 2, 4, 6, and 15 m/sec) and low pressures (0.27, 0.54, 0.8, 1.1, 1.35, 1.47, and 2.7 MPa) in air. In view of the high friction coefficient and large wear, the composite materials cannot be proposed as antifriction ones for operation at small sliding velocities and low pressures. The titanium-based composites are promising as antifriction materials at an increased sliding velocity (15 m/sec) and low pressures when their friction coefficients range from 0.3 to 0.36 and wear ranges from 1.91 to 68.3 mg/km. In dry friction at a high sliding velocity in air, the temperature of their working surface increases resulting from the formation of titanium oxides and then a dense secondary lubricating microheterogeneous film. The composition and structure of the secondary films differ from those of the starting materials and determine their antifriction properties and friction performance.

Effect of composition and sintering temperature on mechanical properties of ZrO2 particulate-reinforced titanium-matrix composite

The titanium-based composites were synthesized by powder metallurgy method. The effects of composition and sintering temperature on the microstructure and properties of the titanium-based composites were investigated by X-ray diffraction, optical microscopy, scanning electron microscopy and mechanical properties tests. The results demonstrate that adding ZrO2 particles can improve the mechanical properties of powder metallurgy (P/M) titanium-based composites. The Ti composite with 4% (mole fraction) ZrO2 sintered at 1100 °C for 4 h shows an appropriate mechanical property with a relative density of 93.9%, a compressive strength of 1380 MPa (570 MPa higher than pure Ti) and good plasticity (an ultimate strain above 24%).

Microstructure and Properties of Ti-8Mo-12Fe and Ti-8Mo-8Cu alloys with Cr3C2 Additives Produced in the Powder Metallurgy Processes

Titanium base composites with a 3% wt of Cr3C2 additives were processed by powder metallurgy using vacuum sintering between 1423∼1523K. Different elements of the alpha-beta type Ti alloys were compared. Fe-based alloys accelerate the sintering process. Mo proves to be a good candidate for solution strengthening and Cu effectively increase the material ductility of the Ti matrix. Therefore Cr3C2 and Mo are both very suitable β stabilized additives for reinforcing Ti-based composites. The development of the plastic deformation of the ternary alloys has been observed and the morphology of the eutectic alloy Ti-8Mo-8Cu causing refinement and supersaturating of the β phase is crucial factor for improving the ductility of the Ti alloys. On the contrary Ti-8Mo-12Fe induced a change of the morphology of the eutectic and increase fraction. The aim of this project is to compare the sintering behavior and evolving phases using SEM images taken from polished specimens and bending testing fractured surfaces.

Microstructure development on sintered Ti/HA biocomposites produced by powder metallurgy

Titanium-based composites with in-situ calcium and phosphor phases were prepared by powder metallurgy processing with titanium and hydroxyapatite (HA) powders. The mixtures were performed in a friction mill with alcohol for 5 hours, dried in a rotating evaporator, pressed at 600 MPa and sintered at 1200 ºC for 2 hours in argon atmosphere. Crystal phases of the as-fabricated composite are found to be, α-Ti, CaTiO3, Ca3(PO4)2 and Ti xPy phase(s). The analyses revealed that titanium particles were covered with a compact layer of Ti xPy and CaTiO3 phases, which resulted from the decomposition of HA into CaTiO3 and β-Ca3(PO4)2 at approximately 1025 ºC. Then the reactions were followed by the decomposition of β-Ca3(PO4)2, resulting in the growth of CaTiO3 layer and in the nucleation and growth of Ti xPy phase(s).

Assessment of interface deformation and fracture in metal matrix composites under transverse loading conditions

The transverse properties of unidirectional metal matrix composites (MMCs) are dominated by the fiber/matrix interfacial properties, residual stresses and matrix mechanical response. In order to monitor and study, in situ, the failure of interfaces in titanium-based composites subjected to transverse loading conditions, an ultrasonic imaging technique has been developed. The interface was imaged ultrasonically and the change in ultrasonic amplitude with the transverse loading was monitored, indicating the sensitivity of the technique to fracture and deformation of interfaces. This change in amplitude has been explained in terms of the multiple reflection theory of ultrasonic waves. The multiple reflection theory enabled estimation of the interfacial deformation and debonding as a function of loading. The ultrasonic technique was also used in conjunction with finite element modeling in order to quantify the fiber/matrix interfacial transverse strength in situ in MMCs.

Titanium-Based Metallic Glass Composites with Good Plasticity

Three types of Ti-based alloys (an amorphous material, an amorphous composite with intermetallic crystals, and an intermetallic compound) of the compositions Ti41.5Zr2.5Hf5Cu42.5−x Ni7.5+x Si1 (x = 0, 5, and 15) were fabricated to study the effect of composition on glass formability and microstructure, and the dependence of mechanical properties on microstructure were investigated at room temperature. The results show that the amorphous composite has an excellent combination of both ultrahigh strength (2245 MPa) and large plastic strain (9 pct), which is a significant improvement compared to both the fully amorphous and intermetallic structures. In addition, it is also found that the crystal phases in the amorphous matrix can obstruct the shearing-off of the shear bands by inducing them to interact, deflect, and branch, resulting good plasticity in the amorphous composite.

Characterization of Interphase Environmental Degradation at Elevated Temperature of Fibre-Reinforced Titanium Matrix Composites

Fibre reinforced metallic composite materials are being considered for a number of applications because of their attractive mechanical properties as compared to monolithic metallic alloys. An engineered interphase, including the bond strength between the composite's constituents, contributes to a large extent to the improvement of strength and stiffness properties of this class of materials. However, in high temperature applications, where combination of cyclic loading with environmental effects is expected, consideration should be given to interphase degradation, especially in the vicinity of stress risers, such as notches and holes. The applicability of damage tolerance analysis in structural components made of titanium matrix composite materials designed to operate under high temperature environments would depend on the availability of adequate characterization methods for the evaluation of interfacial degradation. The objective of this paper is to provide a basic understanding of interfacial degradation mechanisms due to oxidation in environmentally exposed titanium-based composites subjected to cyclic stresses. A non-destructive method has been developed enabling high-resolution monitoring of interfacial damage initiation and accumulation as well as surface/subsurface cracking behaviour during interrupted fatigue tests. This nondestructive technique is based on surface acoustic wave propagation in the composites and can detect minute changes in elastic properties of the interfacial region due to elevated temperatures as well as oxygen effects.

Sintering and Mechanical Properties of Titanium-Based Metal-Ceramic Composites Produced from Reduction of Titanium Dioxide

Sintering and Mechanical Properties of Titanium-Based Metal-Ceramic Composites Produced from Reduction of Titanium Dioxide