As-received Ti Research Articles

Strength-ductility synergy in twinned titanium fabricated via dynamic equal channel angular pressing and heat treatment

Dynamic equal channel angular pressing (DECAP) and heat treatment are applied to pure Ti to achieve a strength-ductility synergy. DECAP induces a complex multiscale twin structure in Ti including four primary twin types, secondary twins and tertiary twins with multiple variants, and an increased yield strength (58% higher than the as-received Ti). Subsequent annealing at 200 ℃ and 400 ℃ leads to improved ductility and strength. The yield strength (σy) and total elongation (ɛt) for the Ti sample processed with DECAP and 400 ℃ annealing are 555 MPa and 30%, respectively, and its σyɛt product is ∼45% higher than the as-received Ti. DECAP and subsequent annealing lead to a superior strength-ductility synergy in twinned Ti, providing a novel approach to produce high strength and ductility materials via dynamic deformation and subsequent heat treatment.

Tailoring microstructure and mechanical properties by laser powder bed fusion of Ti powder recycled and treated via discharge plasma modification

Powder properties are vital to the realization of high-performance metallic components via laser powder bed fusion (LPBF). However, metallic powder recycled during LPBF exhibits out-of-specification properties, thus causing components subjected to LPBF to possess inferior tensile ductility. Hence, we devise a discharge plasma modification (DPM) method to heal out-of-specification Ti powder recycled during LPBF, which can be used to manufacture high-performance bulk Ti via LPBF. The hexagonal ω-phase, which is present during the LPBF of as-received Ti powder and is caused by low O contents and high laser pressures, reappears during the LPBF of recycled and DPMed Ti powders. Bulk Ti subjected to LPBF possesses excellent tensile strength and ductility that are comparable to those of metallic Ti processed via various methods. Our results provide an inexpensive method for sustainable recycling metallic powders and manufacturing high-performance metallic components using LPBF.

Effect of cutting speed on shear band formation and chip morphology of Ti–6Al–4V alloy using nanoindentation and EBSD mapping

The hardness and orientations of the primary α grains (αp) and the transformed β (βt) grains in segmented chips obtained by turning an as-received solution treated-and-aged bar of Ti–6Al–4V (wt.%) at cutting speeds of 1, 1.5 and 2 m/s (61, 91, and 122 m/min) were analyzed using nanoindentation mapping and electron backscattered diffraction (EBSD) maps. The hardness of each αp grain in the as-received Ti–6Al–4V bar highly depends on the crystal orientation, varying from 4.5 GPa to 6.7 GPa, and the hardness values of βt were about 20% lower. In the machined chips, αp grains showed hardness values similar to the as-received material while βt became slightly harder. The homogeneous shear strain within the segments (between shear bands) was estimated to be around 0.4–0.7 at all three cutting speeds. The width of the shear bands in the 1 and 1.5 m/s chips were ∼1.3 μm and ∼2 μm in the 2 m/s chips, which are 10–40% of thicknesses predicted by Molinari's isotropic continuum model, respectively. A smaller homogeneous shear strain was correlated with larger shear cracks at each cutting speed. Grain orientations favored by prism ⟨a⟩ slip in αp when cutting at 1 m/s made the localized shear band less “adiabatic” since both the shear stress and strain were lower when these orientations were dominant. In contrast, in orientations that favored pyramidal <c+a> slip, the αp grains experienced much higher shear stress and more localized shear strain when cutting at 2 m/s, leading to higher temperatures that were much more likely to induce the α to β phase transformation. A transformation to soft β phase during shearing accelerates plastic instabilities. These observations and comparisons with finite element simulations indicate that temperatures reached the α+β phase field locally, and higher cutting speeds led to more β phase that is detrimental to the tool life.

Multi-wire arc additive manufacturing of Ti basic heterogeneous alloy: Effect of deposition current on the microstructure, mechanical property and corrosion-resistance

Deposition current during fabrication plays an important role in the microstructure and properties of titanium alloy components prepared by multi-wire arc additive manufacturing (MWAAM) technology. In this study, Ti basic heterogeneous alloy with Ti-6.5Al-3.5Mo-1.5Zr-0.3Si (TC11) as the main component was deposited using the MWAAM method with the deposition current ranging from 360 A to 400 A. The effects of deposition current on the microstructural evolution, mechanical and corrosion properties of the MWAAM titanium alloys were investigated, and the process-microstructure-property relationship was analyzed. The results show that the microstructure of as-received Ti basic heterogeneous alloy was mainly composed of lamellar primary α phase (α P ) and transformed β phase (β T ), and increasing the deposition current during the MWAAM process would result in the increased width of α phase and the decreased aspect ratio of α phase. The mechanical properties of MWAAM-deposited specimens decrease with increasing current, which means that phase composition played a dominant role in determining hardness. When increasing the deposition current during the MWAAM process the ultimate tensile strength (UTS) decreased from 843.75 to 804.38 MPa. The MWAAM-deposited Ti basic heterogeneous alloy featured excellent corrosion properties, the corrosion potential of the best specimen was − 311 mV SCE and the corrosion current density was 1.23 × 10 −8 Acm −2 . This study provides a better understanding of the effect of deposition current on the targeted deposition property in the MWAAM process, which will contribute to future process control, improvement and optimization. • MWAAM-deposited Ti basic heterogeneous alloy was prepared by various deposition current. • Microstructure features and property was correlated with deposition current. • Deposition current of the Ti basic heterogeneous alloy was shown to affect the α + β microstructure.

Evaluation of the inflammatory and osteogenic response induced by titanium particles released during implantoplasty of dental implants

Implantoplasty is a mechanical decontamination technique that consists of removing the threads and polishing and smoothing the dental implant surface. During implantoplasty there is a large release of titanium metal particles that might provoke a proinflammatory response and reduce the viability of osteogenic cells. We analyze the inflammatory and osteogenic response induced by Ti6Al4V particles released during implantoplasty and by as-received commercially pure Ti particles. Macrophages stimulated with metal particles obtained by implantoplasty and with as-received Ti particles showed an increased proinflammatory expression of TNF-α and a decreased expression of TGF-β and CD206. Regarding cytokine release, there was an increase in IL-1β, while IL-10 decreased. The osteogenic response of Ti6Al4V extracts showed a significant decrease in Runx2 and OC expression compared to the controls and commercially pure Ti extracts. There were no relevant changes in ALP activity. Thus, implantoplasty releases metal particles that seems to induce a pro-inflammatory response and reduce the expression of osteogenic markers.

Nondestructive Texture Measurement of As-Received Ti Alloy Tubing via Simultaneous Shaping and Tilting Defocusing Correction

During the traditional process of texture testing, the sample to be tested must be flat. Generally, it is quite complicated and difficult to prepare the texture sample for the x-ray diffraction examination since it usually adopts time-consuming corrosion flattening or slice sticking for tubing. In this work, a new method is proposed to measure the texture of curved tube directly by using Eulerian Cradle installed on the x-ray diffractometer. This nondestructive method is favorable for a special defocusing correction sample composed of pure Ti powders with the same curvature radius as that of the tested Ti alloy tubing, and can be used to correct the strength loss caused by the elongated x-ray spot during the tube testing. It is verified that this nondestructive testing method is valid and feasible as compared to the traditional corrosion flattening method of tubing texture measurement. Moreover, this nondestructive testing method is highly effective, more accurate, and time-saving, which can be used for the rapid texture measurement for Ti alloy tubes.

Development of in situ composites via reactive friction stir processing of Ti–B4C system

In situ titanium matrix composites were fabricated by introducing an exothermic reaction between Ti and B4C during friction stir processing (FSP). Formation of TiB, TiB2, and TiC was confirmed by X-ray diffraction and transmission electron microscopy along with energy dispersive X-ray spectroscopy and diffraction pattern. TiB and TiB2 whiskers and TiC particles influenced the dynamic recrystallization process, which facilitated an equiaxed grained structure rather than the Widmanstätten microstructure. Mechanical properties of as-received Ti–6Al–4V including hardness, elastic modulus, compressive yield strength and work-hardening rate (stage B) were improved by ∼ 57%, 17%, 47% and 100%, respectively, after FSP with B4C.

Improvement on electrochemical performances of nanoporous titania as anode of lithium-ion batteries through annealing of pure titanium foils

The effect of annealing of Ti foils before anodization on the morphology and electrochemical performance of resultant nanoporous anatase TiO2 (np-TiO2) as anode in rechargeable lithium-ion batteries (LIBs) was investigated. The np-TiO2 anode fabricated from annealed Ti foils exhibited higher specific surface area and reduced pore diameter compared to np-TiO2 electrode fabricated from as-received Ti foils. The highly porous np-TiO2 anode fabricated from annealed Ti foils exhibited 1st discharge capacity of 453.25 mAh/g and reduced to 172.70 mAh/g at 1 C current rate after 300 cycles; whilst the np-TiO2 electrode fabricated from the as-received Ti foils exhibited 1st discharge capacity of 213.30 mAh/g and reduced to 160.0 mAh/g at 1 C current rate after 300 cycles. Even after 400 cycles, such np-TiO2 electrode exhibited a reversible capacity of 125.0 mAh/g at 2.5 C current rate. Compared to the untreated Ti foils, the enhanced electrochemical performance of np-TiO2 anode fabricated from annealed Ti foils was ascribed to the annealing-induced removal of residual stress among the Ti atoms. The benefit of annealing process can reduce pore size of as-fabricated np-TiO2.

An investigation in to the mechanical properties of CP Ti/TiO2 nanocomposite manufactured by the accumulative roll bonding (ARB) process

In this study, a commercially pure titanium (CP Ti) sheet was produced by the ARB process. Then, the mechanical properties of monolithic and nanocomposites specimens manufactured using 0.1, 0.3, and 0.5wt% TiO2 nanoparticles as the reinforcement were investigated at different ARB cycles. The results showed improvement in the mechanical properties of specimens with the addition of TiO2 nanoparticles, as their yield strength and ultimate tensile strength were increased by increasing the TiO2 nanoparticles percent. In this regard, the ultimate tensile strength of the monolithic specimen reached to 810MPa, while it was 980MPa, 1040MPa, and 1085MPa after applying 8 ARB cycles for 0.1wt%, 0.3wt% and 0.5wt% nanocomposite specimens, respectively. However, the ultimate tensile strength of the as-received CP Ti sheet was 285MPa. Moreover, the yield strength and the ultimate tensile strength were increased by increasing the number of ARB cycles and the total elongation; on the other hand, in the monolithic and nanocomposite specimens, it was decreased by increasing the number of ARB cycles. Grain refinements due to severe strain, work hardening and TiO2 nanoparticles reinforcements were the main causes accounting for the improved mechanical properties. Recovery and dynamic recrystallization were two phenomena observed via TEM studies in the ARB process, leading to the development of equiaxed grains in the final ARB cycles.

In-situ construction of three-dimensional titania network on Ti foil toward enhanced performance of flexible dye-sensitized solar cells

Three-dimensional titania network was in-situ constructed on Ti foil via sequential acid and hydrogen peroxide treatments. The titania network was pure anatase phase and homogeneously covered on the titanium grain surface, which largely enhanced the roughness of the Ti foil. The as-received Ti foil and the treated one were used as the flexible substrates of DSSCs, and energy conversion efficiencies of 3.74% and 4.98% were obtained, respectively. Such remarkable increment can be ascribed to the good electrical contact between the nanocrystalline TiO2 and the Ti foil, the improved electron percolation pathways and recombination inhibition of electrons in Ti substrate with triiodide ions in electrolyte. Flexible DSSCs based on the treated Ti foil showed relatively good mechanical stability, which exhibited 97.3% retention of the initial efficieny after twenty consecutive bending.

Friction behavior of network-structured CNT coating on pure titanium plate

Friction behavior of the network-structured CNTs coated pure Ti plate was evaluated by ball-on-disk wear test using SUS304 ball specimen under dry condition. The friction coefficient was significantly low and stable compared to the as-received Ti plate with no coating film. CNTs coating film had two important roles; self-lubrication and bearing effects to reduce the friction coefficient and carbon solid-solution hardening to improve the abrasive wear property of Ti plate. The annealing treatment at higher temperature (1123K) was more effective to reduce the friction coefficient than that at lower temperature (973K) because the Ti plate surface was uniformly covered with CNTs film even after sliding wear test. This is due to TiC interlayer formation via a reaction between Ti plate and carbon elements originated from CNTs during annealing. As a result, a strong interface bonding between CNTs film and Ti plate surface was obtained by higher temperature annealing treatment, and obstructed the detachment of CNTs film during wear test.

Laser surface textured titanium alloy (Ti–6Al–4V) – Part II – Studies on bio-compatibility

The present study concerns a detailed understanding of wear, corrosion and bio-activity behaviors of laser surface textured titanium alloy (Ti–6Al–4V) with line and dimple geometry developed by ArF excimer laser at a wavelength of 193nm with a pulse length of 5ns. The mechanical properties of the surface have been evaluated by measuring nano-hardness and wear resistance. The corrosion resistance property has also been evaluated in Hank's solution. The effect of laser surface texturing on bioactivity and cell attachment has also been studied. Laser surface texturing led to an increase in nano-hardness to a value of 4–6GPa as compared to 2GPa of the as-received Ti–6Al–4V. Furthermore, laser modified surfaces showed a significant increase in wear resistance and a marginal change in corrosion resistance. Textured surface shows a significant improvement in bioactivity in terms of calcium phosphate deposition rate in Hank's solution. XTT result shows, comparable cell viability of laser textured Ti–6Al–4V as that of as received Ti-alloy. Cell attachment study shows a reduced cell density in textured surface with a maximum reduction in dimple textured surface. Cells aligned themselves along the direction of texturing in linear textured surface.

Laser surface textured titanium alloy (Ti–6Al–4V): Part 1 – Surface characterization

In the present study, a detailed study of the characterization of laser-surface textured titanium alloy (Ti–6Al–4V) with line and dimple geometry developed by using an ArF excimer laser operating at a wavelength of 193nm with a pulse length of 5ns is undertaken. The characterization of the textured surface (both the top surface and cross section) is carried out by scanning electron microscopy, electron back scattered diffraction (EBSD) technique and X-ray diffraction techniques. There is refinement of microstructure along with presence of titanium oxides (rutile, anatase and few Ti2O3 phase) in the textured surface as compared to as-received one. The area fractions of linear texture and dimple texture measured by image analysis software are 45% and 20%, respectively. The wettability is increased after laser texturing. The total surface energy is decreased due to linear (29.6mN/m) texturing and increased due to dimple (67.6mN/m) texturing as compared to as-received Ti–6Al–4V (37mN/m). The effect of polar component is more in influencing the surface energy of textured surface.

Growth of TiO2 Nanotube Layers on Ti Substrates with Different Microstructures

Since the reports on self-organized tubular oxide layers on Ti and its alloys by Assefpour-Dezfuly et al[1] and Zwilling et al[2,3], TiO2 nanotube layers have been widely studied in several application fields owing to its unique chemical and physical properties. It was reported that the morphology of the oxide layers is strongly influenced by anodization parameters such as electrolytic composition, applied voltage and electrolyte temperature. However, among the many anodization parameters, the influence of titanium substrate on oxide layer growth has not been clear yet. In the present study, the growth behavior of nanotubular oxide layers was examined by using Ti substrates with various microstructures. As-received Ti sheets (purity: 99.5%) were heat-treated at 500 °C for 12 h to ensure homogeneity. After the homogenization, some Ti sheets were heat-treated at various temperatures in argon atmosphere. Also, the other sheets were subjected to ARB (Accumulative Roll Bonding) process up to 6 cycles to change the microstructures. Anodization was carried out at 50 V for 3 h in ethylene glycol containing 2 wt% H2O and 0.05 M NH4F. After the anodization, the morphology of oxide layers was characterized by FE-SEM. Nanotubebular oxide layers were formed on all Ti sheets whereas the growth of nanotubular oxide layer was affected by the microstructure of Ti substrate that can be controlled by heat treatment and ARB process. The grain size increased with increasing heat-treatment temperature, duration while increasing the number of ARB cycle decreased the grain size. Consequentially, nanotubular oxide layer thickness increased with decreasing grain size. Therefore, it was found that the growth behavior may be affected by the numerous lattice defects in substrate introduced by heat-treatment and ARB process.

Texture of friction stir welded Ti–6Al–4V alloy

The α+β titanium alloy, Ti–6Al–4V, was welded by friction stir welding using a W–Re pin tool, and the defect-free weld was produced with proper welding parameters. Texture of the Ti–6Al–4V friction stir weld was studied by orientation imaging microscopy. The as-received Ti–6Al–4V sheet mill annealed was composed of elongated primary α and transformed β. A typical rolling texture was observed in the base material. The microstructure of the stir zone was significantly different from that of the base material. The stir zone was characterized by the presence of considerable amount of equiaxed dynamically recrystallized grains and a texture around {φ1=30°, ϕ=62°, φ2=30°} was developed during the friction stir welding.

Tribological Properties of Titanium Plate Coated with Carbon Nanotubes

This study investigated the tribological property and wear behavior of pure titanium (Ti) plate coated with un-bundled multi-walled carbon nanotubes (MWCNTs). The network-structured MWCNT films were formed on Ti substrate, and their tribological properties were examined by the ball-on-disk wear test equipment under dry sliding condition. SUS304 stainless steel ball was used as a counterpart material in this test. The mean friction coefficient of the Ti plate coated with MWCNTs was remarkably lower and stable compared to the as-received pure Ti plate without any coating films. SEM-EDS analysis showed the network-structured MWCNT films obviously remained after wear test for 3.6 ks in sliding and no seizure phenomena with the SUS304 ball. The above excellent tribological performance was due to CNTs self-lubricant, their bearing effects and the strong metallurgical bonding between Ti plate and MWCNT films by annealing.

Indentation and scratch testing of DLC-Zr coatings on ultrafine-grained titanium processed by high-pressure torsion

High-pressure torsion was employed to refine the microstructure of grade 2 Ti under an imposed pressure of 3.0GPa at room temperature. The microhardness of grade 2 Ti increased from 1.82GPa for the coarse grain state to 3.05GPa after high-pressure torsion processing, where this value is very close to the hardness of the Ti–6Al–4V alloy. Subsequently, several diamond-like carbon (DLC) coatings with thicknesses of ∼1.4μm were deposited on as-received Ti, high-pressure torsion processed Ti and Ti–6Al–4V samples via physical vapour deposition. Both indentation and scratch tests showed a much improved adhesion of DLC-7Zr, DLC:H-7Zr and DLC-9Zr coatings with high-pressure torsion processed Ti as the substrate by comparison with the same coatings on coarse-grained Ti. The results suggest that commercial pure Ti processed by high-pressure torsion and coated with a diamond-like carbon coating provides a potential candidate material for bio-implant applications.

Influence of interfacial defects on the impact toughness of solid state diffusion bonded Ti–6 Al–4 V alloy based multilayer composites

Microstructure and mechanical properties, with emphasis in impact toughness behaviour, of two multilayer composites have been investigated. The multilayer materials are constituted by thirteen layers of high strength Ti–6Al–4V alloy. Stacked layers have been successfully joined by diffusion bonding considering two processing temperatures, 750 and 900°C. The proportion of α/β phase in the microstructure during diffusion bonding process determines the presence of pores at the interface, and therefore the mechanical properties of the composite material. Higher bcc β phase proportion during diffusion bonding process at the highest temperature of 900°C leads to high bonding degree, without noticeable toughness increase of the multilayer composite. In contrast, higher proportion of harder hcp α phase at 750°C makes difficult the healing of interfacial pores, decreasing interfacial toughness and leading to a toughness value of the multilayer composite seven times higher than the reported value for the as-received Ti–6Al–4V alloy.

Texture evolution and anisotropy in the thermo-mechanical response of UFG Ti processed via equal channel angular pressing

The texture evolution and thermo-mechanical response of grade 1 titanium after equal channel angular pressing (ECAP) at different strain rates and temperatures were measured. As-received Ti was processed via ECAP at 275°C for up to four passes using route BC. The uniform microstructure from the as-received condition, goes from long, coarse bands with some grains relatively undeformed after a single pass to mostly uniform fine and ultrafine grains after four passes. The texture of the as-received Ti was of a typical cold-rolled plate. The basal plane normal direction stayed perpendicular to, and rotated about, the longitudinal direction of the billet during all numbers of passes. The mechanical response of UFG Ti, subjected to four passes, was determined at −196, 22 and 375°C, and at strain rates from 10−4 to 2000s−1 in the different loading directions. It was found that the yield strength and flow stress were different in all three loading directions, at all strain rates and testing temperatures. Macroscopic shear band failure was observed in the samples subjected to dynamic loading, and the onset was dependent on the loading direction and testing temperature. Finally, the anisotropy shows up in the yield strength between tension and compression loading, where it is greater in tension.

Enhanced mechanical properties and in vitro cell response of surface mechanical attrition treated pure titanium

Surface mechanical attrition treatment (SMAT) was used to fabricate nanocrystalline surface layers on the commercial purity titanium. X-ray diffraction and transmission electron microscopy results indicate that the top layer contained nanograins. Enhanced strength and microhardness were achieved due to the surface nanostructure. Cell culture tests have shown a greater adhered cell density and more extensively spreading morphologies of Saos-2 cells on the SMAT substrates compared to those on the as-received Ti counterparts. Enhanced cell viability and cell cycle were also achieved on the SMAT Ti substrates. These could be attributed to the nanostructure grains with the increased surface hydrophilicity and roughness on the SMAT Ti.