CP Ti Research Articles

The influence of powder morphology on the microstructure and mechanical properties of as-sprayed and heat-treated cold-sprayed CP Ti

The influence of powder morphology on the microstructure and mechanical properties of as-sprayed and heat-treated cold-sprayed CP Ti

Improved Biocompatibility of TiO2 Nanotubes via Co-Precipitation Loading with Hydroxyapatite and Gentamicin

The antibacterial properties of titanium make it useful for clinical applications. Hydroxyapatite (HA) is widely utilized as a coating on orthopedic implants to improve osteointegration. Titanium oxide nanotubes (TNT) are recognized as a promising solution for local antibiotic therapy in bone implants. It is demonstrated that the utilization of HA-coated titanium can improve the biocompatibility of bone implants. This research aims to examine the antibacterial properties and biocompatibility of the TiO2 nanotubes by loading HA and gentamicin. In vitro testing, the characterization of drug release, cell adhesion and proliferation, bacteria culture, and antibacterial tests were conducted. During the in vivo experiments, Staphylococcus aureus was implanted into the femur of rats. The animals were sacrificed at four weeks followed by microbiological and clinical assessments on the bone, which were conducted by removing the implants followed by agar plating. The in vitro cell incubation demonstrated that the TiO2 nanotubes loaded with hydroxyapatite and gentamicin had better cellular compatibility compared to Cp–Ti. In addition, in vitro elution testing showed that gentamicin was released from the hydroxyapatite/TiO2 nanotubes for as long as 22 days. The release time was much longer than the TNT loaded with gentamicin at only 6 h. All animals in the gentamicin/HA/TNT group were free of infection compared to those in the Cp–Ti, TNT, and HA/gentamicin/TNT groups. There was a considerable reduction in the rates of infection among the rats with gentamicin-HA-TNT coatings compared to standard titanium. These results indicated that the co-precipitation of gentamicin and HA loading using the TNT method provided a novel prophylactic method against prosthetic infections and other biomedical applications.

Tailoring the deformation characteristics of commercial purity titanium through hot deformation of a martensitic microstructure

The control of microstructure, texture and deformation inhomogeneity is critical for the hot working of titanium alloys and to optimize their mechanical properties. Herein, a new approach to control the grain refinement, texture and deformation anisotropy of commercial purity titanium (CP–Ti) was established through hot working of a martensitic starting microstructure. The deformation characteristics of the martensitic CP-Ti were investigated through uniaxial hot compression testing at 800 °C and compared with the same alloy with an equiaxed starting microstructure. The associated microstructure, texture development and grain refinement mechanisms were elucidated using electron backscatter diffraction (EBSD) and flow behavior analysis. The equiaxed microstructure displayed a typical flow behaviour of metals undergoing continuous dynamic recrystallization (CDRX). This was accompanied by moderate grain refinement to ∼8.2 μm and macroscopically non-uniform expansion of specimen. In comparison, the martensitic microstructure revealed a stress-strain curve of continuous softening beyond the peak strain. An enhanced grain refinement to ∼5 μm was obtained also via CDRX in the form of kinking of laths and progressive lattice rotation without noticeable macroscopic deformation anisotropy. This distinct deformation behaviour was mainly attributed to the unique microstructure and texture formed through the martensitic transformation, which altered the activation of slip systems, grain refinement kinetics and texture development during hot deformation.

Effect of Mo content on Ti-Al-Mo ternary alloys for biomedical applications

The microstructure, microhardness, nano hardness, wear-resistance, and anti-wear properties of Ti6AlxMo ternary alloys (x = 3–15 wt%) have been studied for biomedical applications. The microstructural and phase analysis have demonstrated that there is an increase in the β phase with the increase in Mo wt%, while α and α2 phases decrease. Consequently, Ti6Al15Mo alloy has the lowest elastic modulus value. The highest micro and nano hardness values were exhibited by Ti6Al6Mo alloy owing to the presence of alpha and beta colonies with low interlayer distance in the microstructure. The hardness and wear resistance properties of Ti6Al15Mo alloys were comparatively higher than existing biomaterials like Ti6Al4V and CP Ti. The Ti6Al15Mo alloy can be considered as a promising new age biomaterial.

The role of strain rate and texture in the deformation of commercially pure titanium at cryogenic temperature

In this work, we explore the effect of strain rate and crystallographic texture on the hardening behaviour and ductility of grade 2 commercially pure titanium (CP–Ti) plate at both room (298 K) and cryogenic temperature (123 K). EBSD technique was used to characterise the microstructural features and analyse the deformation twins and active slip systems in α-Ti. Using the SEM fractography, the necking resistance was estimated by measuring the reduction of cross-sectional area. As the strain rate decreases, the elongation was improved with the enhancement of strain-hardening and necking resistance, whereas this behaviour was relatively strain rate insensitive at 298 K. Consequently, the total elongations were increased from 38% (298 K) to 65% (123 K), and from 28% (298 K) to 35% (123 K) in tension parallel and transverse to the rolling direction of the plate, respectively. The combined effect of strain rate and (cryogenic) temperature affected the transition of deformation mechanisms involved in the twinning and dislocation slip, thereby leading to the three or four multi-stage strain-hardening behaviour. The results reveal that in addition to the dislocation slip, the deformation twinning contributed to the strain-hardening, and improvement of total elongation of α-titanium at cryogenic temperature.

Synthesis and characterization of self-organized TiO2 nanotubes grown on Ti-15Zr alloy surface to enhance cell response

In recent years, studies have been shown that the presence of TiO2 nanotubes on the titanium alloy surfaces could induce the enhancement of the cell adhesion on the titanium alloys surface. In the present study, the cell response of the surface of the Ti-15Zr alloy after TiO2 nanotubes growth (NTs) via anodic oxidation was evaluated. TiO2 NTs were obtained in organic electrolytes and analyzed after annealing using Scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy. The attachment and growth of adult human adipose-derived stem cells (ADSCs) were considered for 1 and 7 days for better annealing conditions (450°C). Besides, the influence of the TiO2 NTs growth on the corrosion resistance and Staphylococcus epidermidis bacterial adhesion was evaluated. Results indicated that a self-organized and homogeneous layer of TiO2 nanotubes was formed. XRD analysis and SEM micrographs confirmed that as-anodized, amorphous nanotubes crystallized into anatase phase at 450°C. According to electrochemical analysis, Ti-15Zr alloy exhibited better corrosion resistance compared to commercially pure titanium (cp Ti), but there was no significant difference in passivation capacity between samples evaluated before and after anodization. It was observed that an increase in cellular adhesion and no significant difference in bacterial proliferation occurred despite the presence of TiO2 nanotubes which changed the surface roughness.

Uniformly dispersing GNPs for fabricating graphene-reinforced pure Ti matrix composites with enhanced strength and ductility

The uniform dispersion of graphene nanoplatelets (GNPs) in the titanium matrix is essential but challenging for preparing high-performance graphene-reinforced titanium matrix composites. This study conveniently dispersed GNPs uniformly in commercial pure titanium (CP Ti) powders by in-situ exfoliating GNPs from high-purity graphite balls via 3D vibration milling and fabricated graphene-reinforced titanium matrix composites (in-situ GNPs/Ti) with improved strength and ductility. Besides, the purchased GNPs were ex-situ introduced into CP Ti through 3D vibration milling as a comparison to investigate the effect of different carbon sources on the uniformity of GNPs distribution. Compared with CP Ti, the ultimate tensile strength, yield strength, elongation, and microhardness of the in-situ GNPs/Ti composite were improved by 42.8%, 20.2%, 12.6% and 9.6%, respectively. The improvements in mechanical properties were mainly attributed to the load transfer of the uniformly dispersed GNPs and the pinning effect of in-situ generated titanium carbide (TiC). Furthermore, it is benefited from considerable strengthening efficiency in this work, the high-purity graphite balls were verified to be a befitting carbon source for 3D vibration milling to introduce GNPs into composites. It could be generalized to fabricating other metal matrix composites reinforced with graphene.

Electrical stimulation of titanium to promote stem cell orientation, elongation and osteogenesis

Electrical stimulation of cells allows exogenous electric signals as stimuli to manipulate cell growth, preferential orientation and bone remodelling. In this study, commercially pure titanium discs were utilised in combination with a custom-built bioreactor to investigate the cellular responses of human mesenchymal stem cells via in-vitro functional assays. Finite element analysis revealed the homogeneous delivery of electric field in the bioreactor chamber with no detection of current density fluctuation in the proposed model. The custom-built bioreactor with capacitive stimulation delivery system features long-term stimulation with homogeneous electric field, biocompatible, sterilisable, scalable design and cost-effective in the manufacturing process. Using a continuous stimulation regime of 100 and 200 mV/mm on cp Ti discs, viability tests revealed up to an approximately 5-fold increase of cell proliferation rate as compared to non-stimulated controls. The human mesenchymal stem cells showed more elongated and differentiated morphology under this regime, with evidence of nuclear elongation and cytoskeletal orientation perpendicular to the direction of electric field. The continuous stimulation did not cause pH fluctuations and hydrogen peroxide production caused by Faradic reactions, signifying the suitability for long-term toxic free stimulation as opposed to the commonly used direct stimulation regime. An approximate of 4-fold increase in alkaline phosphatase production and approximately 9-fold increase of calcium deposition were observed on 200 mV/mm exposed samples relative to non-stimulated controls. It is worth noting that early stem cell differentiation and matrix production were observed under the said electric field even without the presence of chemical inductive growth factors. Statement of significanceThis manuscript presents a study on combining pure titanium (primarily preferred as medical implant materials) and electrical stimulation in a purpose-built bioreactor with capacitive stimulation delivery system. A continuous capacitive stimulation regime on titanium disc has resulted in enhanced stem cell orientation, nuclei elongation, proliferation and differentiation as compared to non-stimulated controls. We believe that this manuscript creates a paradigm for future studies on the evolution of healthcare treatments in the area of targeted therapy on implantable and wearable medical devices through tailored innovative electrical stimulation approach, thereby influencing therapeutic conductive and electroactive biomaterials research prospects and development.

Development of Ti–Zr alloys by powder metallurgy for biomedical applications

ABSTRACT Commercial pure titanium offers excellent biocompatibility, but its properties are poor for some biomedical applications where both mechanical properties and biocompatibility are required. The study attempts to evaluate the developement ofTi–Zr alloys using conventional powder metallurgical techniques by mixing elemental powder (BE) or mechanical mixing (MA) as a function of the zirconium content (6, 15 and 20 wt-%). Sintering was performed at 1523 K after compaction at 700 MPa for BE powders and 900 MPa for MA powders. Sintered parts were tested to obtain maximum flexural strength. Samples were characterised microstructurally by X-ray diffraction to study the phases. Optical microscopy (OM) and scanning electron microscopy (SEM) were performed to study the phases, porosity, grain size. Flexural strength to Ti CP was greater, but slightly diminished with increasing Zr content. However, the elastic modulus increased slightly compared to Ti. The results obtained show that it is possible to make these alloys by powder metallurgy.

Effect of grain size on the ductile-brittle fracture behavior of commercially pure titanium sheet metals

Fabrication of miniaturized titanium thin-walled products directly using sheet metals is proven to be a promising approach with high productivity. In this process, however, there are many unknowns in terms of size effect and its affected fracture behavior. This study is thus aimed at investigating the effect of grain size on the fracture behavior of commercially pure titanium (CP–Ti) sheets with a thickness of 0.1 mm. Tensile tests combined with a digital image correlation (DIC) measurement system were conducted to determine the critical fracture stress of the specimens with different grain sizes. The fracture morphologies of the stretched specimens were further characterized by a scanning electron microscope (SEM). According to the experimental observation, an evident transition from ductile to brittle fracture as the grain size increases from 33.1 to 107.7 μm is revealed. Macroscopically, the elongation and critical fracture stress decrease with the increase of grain size. While according to the microscopic observations, the number of dimples decreases with the increase of grain size. Meanwhile the cleavage planes and river patterns gradually appear in the coarse grain fracture surface. To explore the fracture mechanism, transmission electron microscope (TEM) observations were made utilizing the specimens with fine and coarse grains. Significant dislocation emission from crack-tips was revealed at different grain sizes. Moreover, evident dislocation pile-up at grain boundaries was observed in the specimen with a grain size of 33.1 μm. Those intense dislocations reduce the effective stress at the crack tip resulting in higher crack propagation resistance. Nevertheless, the dislocation density at crack-tip decreases strongly with the increase of grain size leading to high crack-tip effective stress and less crack plasticity. Thus cleavage fracture was dominated in coarse grain CP-Ti sheets. A dislocation shielding model was developed to capture the dislocation observation in various grain sizes. The critical stress onset of CP-Ti sheets fracture during the tensile test was also predicted for validation.

Microvoids in electrochemically hydrogenated titanium-based alloys

In a recent study, it was observed that electrochemical charging with hydrogen produces microvoids both in wrought and in additively manufactured, electron beam melted (EBM) Ti–6Al–4V alloys. This result is surprising since titanium forms stable hydrides and has an exothermic heat of hydrogen solution. By comparison, hydrogen bubble formation is typically observed only in metals and alloys with an endothermic heat of hydrogen solution that do not form hydrides. Here, we evaluate possible mechanisms for the formation of microvoids and bubbles in Ti-based alloys. Additional experimental work confirms that voids do not form in electrochemically hydrogenated, single-phase, pure wrought Ti, whereas they do form in the wrought Ti–6Al–4V alloy hydrogenated under the same conditions. In commercially pure Ti (CP–Ti), hydride is formed from the surface inward, and the surface is brittle and heavily cracked and disintegrated. By contrast, in the two-phase alloy, hydrides are formed also deeper in the bulk, and microvoids are evident both adjacent to the surface and along interphase boundaries. Alongside the forming hydride, the surface integrity is maintained, although some cracks are formed due to microvoid coalescence. While the incorporation of hydrogen into the alloy causes a large increase in its volume, we note that the precipitation of hydride from a supersaturated solution causes a net contraction. We suggest that the mechanism that best reflects the experimental evidence of microvoids formation is a manifestation of the contraction that results from hydride precipitation from a hydrogen-supersaturated alloy.

Evaluation of Corrosion Behavior by Measuring Passivation Current Density of Dental Implant Coated with Bioceramic Materials.

Background This paper reports the corrosion behavior of uncoated commercially pure titanium and Ti-6Al-4V samples and these coated with hydroxyapatite, partial stabilized zirconia (PSZ), and the mixture of partial stabilized zirconia and hydroxyl-apatite by measuring passivation current density and see if there are any differences between them using electrochemical polarization tests in 37°C Hank's solution. Materials and Methods The electrophoretic deposition method (EPD) was elected to keep the coating materials which are HA, PSZ, and the mixture of 50% HA and 50% PSZ on Cp Ti and Ti-6Al-4V alloy samples. The electrochemical corrosion test was achieved by exposing the coated and uncoated samples to Hank's solution which prepared in the laboratory and measuring the polarization potential, passivation current density, and the open circuit potential for all samples. Results The results indicated that the passivation current density for all Cp Ti and Ti-6Al-4V alloy groups that coated with HA, PSZ, and with mixture of 50/50 HA and PSZ was less than uncoated groups. There are no significant differences between all Cp Ti groups when compared with all Ti-6Al-4 V alloy groups. The open circuit potential (OCP) for both Cp Ti and Ti -6Al -4V samples was in the following sequence PSZ > HA > mixture of HA and PSZ > uncoated. Conclusions Coating significantly decreased the passivation current density of Cp Ti and Ti-6Al-4V alloy.

Fracture mechanisms in Ti and Co–Cr growing rods and impact on clinical practice

The widely used treatment of early onset scoliosis based on fusionless spinal instrumentation with growing rods suffers from severe complications due to premature rod failure. Only few studies have explored the fracture mechanisms in single rod constructs, while clinical practice urgently needs guidance. The objectives of this study are (i) to determine the failure mechanisms in Ti–6Al–4V alloy, Ti Cp 2 and Co–Cr alloy rods, and (ii) to propose strategies to reduce the risk of rod fracture. For this purpose, seven rods from three patients treated for early onset scoliosis were characterized by preoperative, pre-fracture X-rays and after-fracture X-rays. Fracture surface analysis, performed using scanning electron microscopy, revealed similar failure mechanisms for all rods, independent of composition and diameter. Fracture is caused by fatigue, associated to repeated bending action in the anteroposterior direction. Cracking initiates at multiple sites. Three-point bending fatigue tests on Ti–6Al–4V bent rods confirmed the fracture scenario. A beam bending model indicates that the failure process is controlled by the combination of cyclic vertical and horizontal forces with amplitudes from 200 N to 400 N and from 70 N to 150 N, respectively. Strategies to minimize fracture involve adaptations of material properties and rod geometry to scoliosis characteristics, including sagittal alignment, and spine behavior.

Solid-state joining of aluminum to titanium: A review

The dissimilar material joining of aluminum and titanium alloys is recognized as a challenge due to the significant differences in the physical, chemical, and metallurgical properties of these alloys, where the increasing demands for high strength and lightweight alloys in aerospace, defense, and automotive industries. Joining these two alloys using the conventional fusion techniques produces commercially unacceptable sound joints due to irregular, complex weld pool shapes, cracking and low strength, high residual stresses, cracks, and microporosity, and the brittle intermetallic compounds formation leads to poor formability or inferior mechanical properties. The formation of intermetallic compounds is inevitable but it is less severe in solid-state than in the fusion welding process. Hence, this article reviews on aluminum–titanium joining using different solid-state and hybrid joining processes with emphasis on the effect of process parameters of the different processes on the weld microstructure, mechanical properties along with the type of intermetallic compounds and defects formed at the weld interface. Among the various solid-state welding processes for aluminum–titanium joining, the following grades of aluminum and titanium alloys were employed such as cp Ti, Ti6Al4V, cp Al, AA1xxx, AA 2xxx, AA5xxx, AA6xxx, AA7xxx, out of which Ti6Al4V and AA6xxx alloys are the most common combination.

Laser Surface Structuring of Commercial Pure Titanium

Aim This Study existent laser surface structuring of commercial pure titanium (Ti) grade II dental implant,surface structuring of the titanium implant expected causing decrease the time of implant healing andaccelerated the periimplant bone formation. So the present study aimed was in vitro evaluation of commercialpure titanium when subjected to two laser surface structuring (dot and groove) in different laser scans andcomparing with titanium surface that not subjected to any surface structuring (control) by using opticalmicroscope, scanning electron microscope (SEM) and X-ray Diffraction analysis (XRD) test.Materials and Methods: CNC fiber laser machine laser was used for performing the structuring on thesurface of the commercial pure titanium (CP Ti) disks and then analyzed with the control group by opticalmicroscope, SEM and XRD test. The study groups are: polished CP Ti (control); (5, 15 and 25) CP Ti withdot design laser scans; (5, 15 and 25) CP Ti with groove design laser scans.Results the optical and SEM results showed a uniform homogenous structure on the surface of the CP Ti forthe two design of all tested laser scans (5, 15 and 25). The XRD results show an increasing in the titaniumoxide layer for the disks with laser structuring comparing to the control one which predicted to increasetitanium osseointegration while maintaining biocompatibility characteristics of the CP Ti.Conclusions: CNC fiber laser machine are successful method for CP Ti surface structuring. For both lasersurfaces structuring design, the 25 laser scan showed more promising results follow by 15 laser scan then 5laser scan and lastly the control group.

Effect of Electric Current Heat Treatment on Commercially Pure Titanium Sheets

Rapid electric current heat treatment has been successfully applied to a cold-rolled sheet of commercially pure titanium (CP Ti). The electric current heat treatment was conducted at various temperatures (400, 500, 600 and 700 °C) by altering the current density (A/mm2). The detailed microstructure and texture evolution was studied using electron backscatter and X-ray diffraction analysis. For comparison, conventional heat treatment at 400, 500 and 600 °C were also applied to the cold-rolled sheets. The electrically heat-treated sample showed a much smaller and uniform grain size with a relatively weak texture than the conventionally heat-treated one. As a result, the electrically heat-treated samples exhibited better tensile properties than conventionally heat-treated samples. Furthermore, the electric current treatment produced minimum sheet distortion and good oxidation resistance compared with the conventional heat treatment.

Breaking bending limit of difficult-to-form titanium tubes by differential heating-based reconstruction of neutral layer shifting

Achieving small-radius bending of difficult-to-form tubular materials with large-diameter, thin-walled (LDTW, D/t > 20) geometry — as well as the properties of high-strength poor-hardening (HSPH) — is a continual target and challenging issue in the aerospace, marine, and healthcare industries. Based on the theoretical analysis of neutral layer shifting reconstruction (NLSR) by positively utilizing the temperature-dependent tension-compression (T-C) asymmetry of tubes, an innovative differential heating-based rotary draw bending (DH-RDB) method is designed, i.e., applying differential working temperatures at the intrados (Tin) and extrados (Tout) of tubes during forming to proactively coordinate the non-uniform deformation and thus prevent multiple forming defects to break the bending limit. To verify the above concept, the temperature-dependent evolution of the T-C asymmetry of titanium tubes was characterised — using commercial pure titanium (CP–Ti) tubes as case materials — and numerically implemented into the thermo-mechanical coupled three-dimensional finite element (3D-FE) model of the DH-RDB process. The influence of two heating schemes–i.e., overall heating and differential heating at the extrados and intrados of the tube — on bending formability was quantitatively assessed regarding multiple bending defects, such as wrinkling, over-thinning, and cross-section flattening. It was found that by introducing differential heating, the design and optimisation space for NLSR in tube bending is enlarged. The overall heating increases the work hardening of titanium tubes and thus restrains wrinkling during bending. Furthermore, the coupling effects of the increased compression-tension flow stress ratio (CTFSR) and decreased friction force under differential heating of Tin < Tout slightly aggravated the inward neutral layer shifting (NLS) but reduced wall-thinning and cross-section flattening. Following the above critical understanding, a series of carefully designed bending experiments were conducted to validate the capability of the DH-RDB to break the bending limit. This proves that the differential heating-based NLSR can be used to positively coordinate T-C non-uniform deformation to break the bending limit of difficult-to-form tubular materials.

Artificial Neural Network Predictive Modelling of Laser Micro-Grooving for Commercial Pure Titanium (CP Ti) Grade 2

Grooving is the process of making a narrow channel on a surface of flat or cylindrical workpiece. Groove is precisely made to parts used in automotive, biomedical, and electronics industries. In automotive industries, groove plays an important role especially on mechanical parts to precisely locate seal (o-ring) to prevent gas/oil leakage between dynamic mating parts. On the other hand, artificial neural network (ANN) has been widely used in developing predictive models of various manufacturing processes to save huge amount of production time and money for industries. Unfortunately, very limited research has been investigated on micro groove quality employing ANN predictive models. Therefore, this research work presents on how the Artificial Neural Network (ANN) predictive model has been established, optimised and utilised to predict the laser micro-grooving quality of commercial pure titanium grade 2 material. A 3KW CO2 laser cutting machine was employed considering laser power, gas pressure, cutting speed, depth of cut and focal distance as the design parameters for modelling. On the other hand, three significant responses namely groove depth, groove width and groove corner radius were investigated. Experimental results were fed to establish the ANN predictive model, which then its parameters were optimized to gain high level prediction accuracy. The predicted results of ANN model presented the mean absolute percentage error for groove depth, groove width and groove corner radius at about 7.29%, 10.93% and 11.96% respectively. The obtained predictive results were found quite promising with the average of mean absolute percentage error (MAPE) for quality predictions which falls between 10 to 15%, concluding the validity of the developed ANN predictive model.

Time Transient of Calcium and Phosphate Ion Adsorption by Rutile Crystal Facets in Hanks' Solution Characterized by XPS.

For the elucidation of the mechanism of calcium phosphate formation on commercially pure titanium (CP Ti) in the human body, rutile TiO2 single crystal plates with (001), (110), and (111) facets, namely, TiO2(001), TiO2(110), and TiO2(111), and polycrystalline plates (TiO2(poly)) were immersed in a simulated body fluid, Hanks' solution (Hanks), for 100-105 s, and the adsorption of calcium and phosphate ions was precisely characterized employing X-ray photoelectron spectroscopy (XPS). Previously published CP Ti data were used for comparison. Prior to immersion in Hanks, oxygen content was more than twice as high as that of titanium due to the existence of hydroxyl groups and water on the oxides. After immersion in Hanks, the composition and chemical state of the TiO2 substrates remained unchanged. Among the electrolytes contained in Hanks, only calcium and phosphate ions were adsorbed by and incorporated onto TiO2 surfaces. Adsorption of calcium ions onto rutile did not exhibit any systematic increase of calcium with immersion time except TiO2(poly). Adsorption of phosphate ions was initially constant, followed by an increase with the logarithm of immersion time. The adsorption rate of phosphate ions decreased in the following order: TiO2(001), TiO2(poly), TiO2(111), CP Ti, and TiO2(110). The coordination number and band gap of each crystal facet of rutile is important for the adsorption and incorporation of phosphate ions. Regular calcium phosphate formation on CP Ti is possibly enabled by the surface oxide film, which consists chiefly of amorphous TiO2. However, calcium phosphate formation kinetics on CP Ti differed from those on the TiO2 crystalline phase. These findings may further the understanding of CP Ti hard tissue compatibility.

Sliding wear behaviour of CP titanium laminates produced by large strain extrusion machining

Titanium sheets find their wide application in aerospace industry. Rolling process is commonly used for making these sheets. Inducing large amount of strain in high strength materials with HCP structure such as Magnesium and Titanium alloys makes rolling a multistage process. Moreover, controlling crystallographic texture in multistage deformation processes is also very critical. To overcome these limitations, in present research attempt large strain extrusion machining (LSEM) process is used to produce laminates from CP titanium sheets with controlled microstructure in a single continuous operation. These CP Ti laminates are produced at different strain rate. Microstructural analysis and hardness measurement of fabricated laminates are carried out using scanning electron microscopy and Vickers microhardness tester respectively. Roughness tester is used for roughness measurement. X-Ray diffraction is used for deformation analysis of the laminates. Sliding wear tests on produced laminates are performed using tribometer. Hardness measurement revealed a ~25–52% increase in hardness value in fabricated laminates as compared to bulk material. This increase in hardness may be attributed to grain refinement resulted from high deformation induced by LSEM process. The surface roughness of fabricated laminates decreased with increase in strain rate. Wear rate analysis of the samples have shown improved wear performance of laminates fabricated by the process in comparison to bulk material. Wear rate is observed to be lower in direction perpendicular to laminate formation direction.