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{001}〈101〉 texture evolution in Ti–37 mol%Nb (Nb–46.5 mass%Ti) alloy was determined under plane strain compression at the temperatures of 800°C, 950°C, and 1100°C, in which preferential dynamic grain growth (PDGG) took place. At lower temperature and higher strain rate such as 800°C–10−2/s, almost no grain growth occurred in the transverse direction (TD), and the α-fiber + near {111}〈110〉 in the γ-fiber texture was developed, which was a stable orientation as deformation texture. At higher temperature and lower strain rate such as 1100°C–10−3/s, the grain growth along the TD remarkably appeared by grain boundary bulging, and an extremely high pole density of the texture near the α-fiber, especially the rotated cube {001}〈101〉, evolved. A planar dislocation structure with pile-ups appeared and individual dislocations were uniformly distributed in the grains. The rotated cube texture fulfills the conditions of the deformation stability and the low Taylor factor in accordance with the PDGG mechanism. The essential aspect of the mechanism is the preferential growth of grains with a stable orientation for deformation and a low Taylor factor in the given deformation mode. [ABSTRACT FROM AUTHOR]

Osseointegration is the basic condition for orthopedic implants to maintain long-term stability. In order to achieve osseointegration, a low elastic modulus is the most important performance indicator. It is difficult for traditional titanium alloys to meet this requirement. A novel β-titanium alloy (Ti–35Nb–7Zr–5Ta)98Si2 was designed, which had excellent strength (a yield strength of 1296 MPa and a breaking strength 3263 MPa), an extremely low elastic modulus (37 GPa), and did not contain toxic elements. In previous in vitro studies, we confirmed the good biocompatibility of this alloy and similar bioactivity to Ti-6Al-4V, but no in vivo study was performed. In this study, Ti-6Al-4V and (Ti–35Nb–7Zr–5Ta)98Si2 were implanted into rabbit femurs. Imaging evaluation and histological morphology were performed, and the bonding strength and bone contact ratio of the two alloys were measured and compared. The results showed that both alloys remained in their original positions 3 months after implantation, and neither imaging nor histological observations found inflammatory reactions in the surrounding bone. The bone–implant contact ratio and bonding strength of (Ti–35Nb–7Zr–5Ta)98Si2 were significantly higher than those of Ti-6Al-4V. The results confirmed that (Ti–35Nb–7Zr–5Ta)98Si2 has a better osseointegration ability than Ti-6Al-4V and is a promising material for orthopedic implants. [ABSTRACT FROM AUTHOR]

Metastable Ti–Nb alloys are promising bone-implant materials due to improved mechanical biofunctionality and biocompatibility. To overcome increasing bacterial infection risk, alloying with antibacterial elements is a promising strategy. This study investigates the effect of minor gallium (Ga) additions (4, 8 wt% Ga) to as-cast and solution-treated β-type Ti–45Nb-based alloy (96(Ti–45Nb)-4Ga, 92(Ti–45Nb)-8Ga (wt.%)) on corrosion and passive film properties, as well as cytocompatibility and antibacterial activity. The electrochemical properties were evaluated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and Mott-Schottky analyses in phosphate-buffered saline (PBS). X-ray photoelectron spectroscopy (XPS) was performed to analyze the chemical composition of passive films. Early adhesion and viability of macrophages and Staphylococcus aureus were assessed by nucleocounting and colony-forming unit counting, respectively. The results showed that high corrosion resistance and passive film properties of Ti–45Nb are retained and even slightly improved with Ga. EIS results revealed that Ga addition improves the passive film resistance. XPS measurements of 92(Ti–45Nb)-8Ga show that the passive film contains Ti-, Nb- and Ga-based oxides, implying the formation of mixed (Ti–Nb-Ga) oxides. In addition, marginal Ga ion release rate was detected under free corrosion conditions. Therefore, it can be assumed that Ga species may contribute to passive film formation on Ga-containing alloys. The 92(Ti–45Nb)-8Ga elicited an antibacterial effect against S. aureus compared to cp-Ti at 4 h. Moreover, Ga-containing alloys showed good cytocompatibility with THP-1 macrophages at 24 h. In conclusion, it was demonstrated that Ga additions to Ti–45Nb are beneficial to corrosion resistance and showed promising initial host and bacterial interactions.

The incorporation of nanoparticles into metallic biomaterials has been recognized as a significant approach to improve their bioactivity for biomedical applications. In this study, friction stir processing (FSP) was employed to incorporate TiO2 nanoparticles as bioactive reinforcement into the β titanium alloy Ti–35Nb–2Ta–3Zr (TNTZ) matrix to construct an integrated micro-nano composite layer. The effect of different TiO2 contents on the osteogenic capacity of rat bone marrow stromal stem cells (BMSCs) was studied. The TiO2/TNTZ composite layer exhibited a refined grain structure with a mean grain size of approximately 10 μm and a characteristic surface morphology of pronounced peaks and valleys with enhanced RSkw and RKur values. Moreover, TiO2/TNTZ significantly promoted the adhesion, proliferation, and spreading of BMSCs, upregulated the expression of genes related to osteogenesis (ALP and Runx2) up to nearly 1.5 times, and enhanced the expression of ALP and OCN (P

The phase composition before deformation is an important factor affecting the deformation mechanism of titanium alloy at room-temperature. In practical production, the initial phase composition can be greatly controlled by changing the solution cooling mode of the alloy, thus affecting the deformation mechanism and mechanical properties of the alloy to a certain extent. Therefore, the study of the effect of solution cooling rate on the deformation mechanism at room-temperature plays an important role in regulating the properties of the alloy. Through room-temperature compression experiments, the microstructure evolution and room-temperature plastic deformation mechanism of Ti–10Mo–1Fe near β-type alloys with different cooling rates after solution treatment at 870 °C were studied in this paper. The results show that the main room-temperature deformation mechanism of the Ti–10Mo–1Fe alloy under rapid cooling conditions (water-cooled) was the {332} twins and stress-induced orthorhombic martensite α″ phase. In addition, a few {112} twins were observed. The plastic deformation mechanism at room temperature under moderate cooling conditions (air-cooled) was primarily {332} twins and dislocation slip. Small numbers of {112} twins were also observed. Under slow cooling conditions (furnace cooling), no new phases are formed during the deformation process, and the plastic deformation mechanism at room temperature is dislocation slip.

Microstructure of novel high-strength metastable β titanium alloy, Ti–4Al–6Mo–2V–5Cr–2Zr, is extremely sensitive to both aging temperature and time length, which directly regulates their mechanical properties. Therefore, it is particularly important to clarify the roles of aging treatment in both microstructure and mechanical properties of Ti–4Al–6Mo–2V–5Cr–2Zr. Through varying the aging temperature from 520 to 640 °C and time from 2 h to 8 h, effects of aging technological parameters on the microstructure and tensile properties of Ti–4Al–6Mo–2V–5Cr–2Zr was systematically investigated. It is noted that the secondary α phase (αs) inside the β matrix coarsens as a function of the aging temperature and time length, and the shape of αs phase changes from fine needle to short rod. Moreover, lower aging temperature and longer aging time result in a higher volume fraction of αs phase. Combined with tensile test results, it is evident that volume fraction of αs phase leads to high strength. The volume fraction of αs phase in the alloy after aging at 520 °C for 6 h reaches 61.9% along with the highest ultimate tensile strength of 1367 MPa. In addition, the strengthening mechanism of reinforced phase αs was clarified with both SEM and TEM observations. Results show that the αs with the internal lattice distortion and HCP structure effectively prevent the dislocation slip. And the αs phase arranged in a triangular shape has a profound strengthening effect.

The production of alloys with high strength and toughness concurrently is still a difficult challenge. Here, we designed a simple solution-ageing heat treatment system to control the morphology and density of α in Ti-15Mo-3Al-2.7Nb-0.2Si via different heat treatment temperatures. The experimental results show that Ti-15Mo-3Al-2.7Nb-0.2Si exhibits a synergistic combination of tensile strength (1364 MPa), plasticity (7.8% elongation), and fracture toughness (101 MPa·m1/2) through solutions in the α/β biphasic region and duplex ageing. Notably, the strength of the alloy after the second step of the ageing process is increased by 15% compared with that after the first step of the ageing process. However, there is less than a 5% reduction in the fracture toughness. TEM observations show that the matrix continues to precipitate denser secondary α during duplex ageing, which causes the strength to increase significantly and causes the fracture toughness to weaken. Our work may provide a novel method to optimize the mechanical properties of alloys by controlling the precipitates. [ABSTRACT FROM AUTHOR]

Osseointegration is the basic condition for orthopedic implants to maintain long-term stability. In order to achieve osseointegration, a low elastic modulus is the most important performance indicator. It is difficult for traditional titanium alloys to meet this requirement. A novel β-titanium alloy (Ti–35Nb–7Zr–5Ta)98Si2 was designed, which had excellent strength (a yield strength of 1296 MPa and a breaking strength 3263 MPa), an extremely low elastic modulus (37 GPa), and did not contain toxic elements. In previous in vitro studies, we confirmed the good biocompatibility of this alloy and similar bioactivity to Ti-6Al-4V, but no in vivo study was performed. In this study, Ti-6Al-4V and (Ti–35Nb–7Zr–5Ta)98Si2 were implanted into rabbit femurs. Imaging evaluation and histological morphology were performed, and the bonding strength and bone contact ratio of the two alloys were measured and compared. The results showed that both alloys remained in their original positions 3 months after implantation, and neither imaging nor histological observations found inflammatory reactions in the surrounding bone. The bone–implant contact ratio and bonding strength of (Ti–35Nb–7Zr–5Ta)98Si2 were significantly higher than those of Ti-6Al-4V. The results confirmed that (Ti–35Nb–7Zr–5Ta)98Si2 has a better osseointegration ability than Ti-6Al-4V and is a promising material for orthopedic implants.

The heat input during laser welding process has significant influence on microstructure and properties of the joints, whereas there is currently limited research concerning the influence of heat input during laser welding process of β titanium alloys. The microstructure and tensile properties of laser welded Ti–3Al–6Mo–2Fe–2Zr (wt.%) joints under different heat inputs were investigated in this paper. Numerical simulation process was used to explain the microstructure evolution in HAZ and fusion zone. The microstructure of HAZ is divided into three different regions from fusion line to base metal. In near-HAZ, mid-HAZ, and far-HAZ, the microstructures are composed of single β phase, β + αp, and β + αp + retained αs, respectively. In fusion zone, the microstructure consists of single β phase because of the fast cooling rate and high content of β stabilizing elements. The ultimate tensile strength (UTS) of laser welded specimens is lower than that of base metal due to the lack of strengthening phase and the coarsening of β grains. Higher heat input further exacerbates the coarsening of β grains in the fusion zone and HAZ, which consequently results in the decrement of UTS of the joints.

Near β titanium alloy is widely used in automotive and aerospace industries due to their high strength-to-weight ratio and high corrosion resistance. The near β titanium alloy can precipitate ω phase and α phase after solution and ageing treatment, the strength of which can be remarkably increased, usually at the expense of ductility. It is one of the most important structural components of load-bearing that usually as aircraft skin, shell plating, main frame, linker and special fastener. The alloy used in this paper is a self-developed Ti-Al-V-Mo-Cr-Zr-Fe-Nb ultra-high-strength β titanium alloy, which is a typical near β titanium alloy. The characteristic of isothermal phase transformation of near β titanium alloys is diversity and complexity, which is sensitive to temperature and directly affects the mechanical properties after ageing. In this paper, the microstructural evolution and mechanical properties of a Ti-Al-V-Mo-Cr-Zr-Fe-Nb ultra-high strength β titanium alloy after isothermal treatment were investigated by scanning electron microscopy(SEM),transmission electron microscopy(TEM) and micro-hardness tester. The results show that only the isothermal ω precipitates are formed during ageing at 300℃, and the size of isothermal ω phases increase with the ageing time. The isothermal ω precipitates are first precipitated during ageing at 400℃. With the extension of the ageing time, the α phase nucleation occurs near the ω/β interface. No α precipitates are obtained in the alloy aged at 500℃, and needle-like α precipitates are directly precipitated from the β matrix, which is evenly distributed in the β matrix in a "V" shape. Tensile test shows that the tensile strength of the alloy is 1716.1 MPa and the elongation is 2% after ageing at 400℃ for 12 h. The tensile strength of the alloy is 1439.8 MPa and the elongation is 9.84% after ageing at 500℃ for 12 h, and has a good combination of strength and toughness.

Oriented to the application of new generation strategic aircraft, M28 (Ti-4Al-5Mo-5 V-6Cr-1Nb) is a novel metastable β titanium alloy with outstanding strength. The research on the machining of such hard-to-machine material remains inadequate. To investigate the machinability of M28, milling experiments were made with the uncoated WC–Co carbide insert. The cutting force and tool life of M28 were compared with those of Ti-6Al-4 V in varying cutting speeds. The tool wear mode was also analyzed. The cutting force of M28 increases with cutting speed significantly, especially in high-speed cutting where it can reach as high as 132% of that of Ti-6Al-4 V. The "transgranular cut" of M28 contributes to the high cutting force. A much shorter tool life in cutting M28, ranging from 0.88% to 13.82% of that of Ti-6Al-4 V, was found in the experiment. Serious edge chipping occurred at the normal cutting speed as the result of stress concentration and abrasion of the secondary α precipitation. In high-speed cutting, chip adhesion, comb cracks, and tool plastic deformation were found at the edge as the result of the high temperature. In addition, the semi-crater at the worn edge tip was formed by the interaction of high-frequency cutting impact, carbide thermal softening, and diffusion wear. A better understanding of the machinability of M28 is conducive to the improvement in manufacture in the aviation industry. [ABSTRACT FROM AUTHOR]

The production of alloys with high strength and toughness concurrently is still a difficult challenge. Here, we designed a simple solution-ageing heat treatment system to control the morphology and density of α in Ti-15Mo-3Al-2.7Nb-0.2Si via different heat treatment temperatures. The experimental results show that Ti-15Mo-3Al-2.7Nb-0.2Si exhibits a synergistic combination of tensile strength (1364 MPa), plasticity (7.8% elongation), and fracture toughness (101 MPa·m1/2) through solutions in the α/β biphasic region and duplex ageing. Notably, the strength of the alloy after the second step of the ageing process is increased by 15% compared with that after the first step of the ageing process. However, there is less than a 5% reduction in the fracture toughness. TEM observations show that the matrix continues to precipitate denser secondary α during duplex ageing, which causes the strength to increase significantly and causes the fracture toughness to weaken. Our work may provide a novel method to optimize the mechanical properties of alloys by controlling the precipitates.

Through room‐temperature compression tests, the microstructure evolution and room‐temperature plastic deformation mechanism of a β‐type Ti–10Mo–1Fe alloy, which exhibits a primary α phase after solution treatment at 780 °C, are studied. When the deformation is small, the existence of the primary α phase makes the distribution of twins between grains uneven. A small amount of intragranular twins grows to the intragranular α phase, and then stops growing. The grain boundary α phase (GBα) plays an important role in inhibiting the growth of twin laths to a certain extent. When the deformation is large, compression cracks appear at the α/β phase interface. The α/β phase interface is weak, and the deformation along the 45° direction is relatively large. Owing to the existence of the primary α phase, the ultimate tensile strength of the alloy increases to 934.5 MPa, and the elongation reaches 21.7%. The room‐temperature plastic deformation mechanism of the Ti‐10Mo‐1Fe alloy solution treated at 780 °C is dominated by {332} <113> twins, as well as by a small amount of {112} <111> twins (0.57%) and stress‐induced orthorhombic martensite α" phase (2.5%). [ABSTRACT FROM AUTHOR]

Copyright of Journal of Materials Engineering / Cailiao Gongcheng is the property of Journal of Materials Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• High cycle fatigue properties of a Ti-4Al-6Mo-2 V-5Cr-2Zr alloy were investigated. • Fatigue cracks tend to nucleate at the α p /β trans and GB α/β trans interfaces in HN. • Fatigue cracks of LM tend to nucleate on the GBs during cyclic loading. • Fatigue life data for HN are more scattered than for LM. To clarify effects of microstructure on fatigue crack initiation mechanism of Ti-4Al-6Mo-2V-5Cr-2Zr alloy, high-cycle fatigue behavior of hierarchical nanostructure (HN) and lamellar microstructure (LM) was investigated. Fatigue tests results show that the high-cycle fatigue property of LM (σ 0.1 (10 7) , 685 MPa) is better than that of HN (σ 0.1 (10 7) , 630 MPa). EBSD analysis and TEM observation demonstrate that with cyclic loading of stress, prism < a > slip is activated in α p phase, and basal < a > slip is activated in grain boundary α phase (GB α). Plastic deformation of HN mainly occurs in short rod α p phase and GB α. Fatigue cracks preferentially initiate at weak parts of these structures and propagate into a transformed β structure (β trans). In addition, the intrinsic reason for the random behavior of the fatigue life can be attributed to differences in the microstructure ahead of the main crack tips. Fatigue data for HN containing GB α and short rod α p shows high scattering. Dislocation slip in LM occurred mainly in β matrix and piled up at α s /β interfaces and grain boundaries (GBs). Local high stresses caused { 0 1 ¯ 11 } nano-scale twins in α s phase to harmonize local plastic deformation, which makes cracks more preferable to nucleate at β GBs. [ABSTRACT FROM AUTHOR]

The solution treated β type Ti-19Nb-1.5Mo-4Zr-8Sn (TNMZS) alloy plate was rolled for minor deformation 2%~8%, followed by low-temperature ageing. The stress-induced α″ martensite and isothermal ω phase was characterized. The results showed that, coherent ω and β phase also satisfied the lattice constant relationships: 2aβ = aω = bω, 32aβ = cω. The pre-deformation caused the rapid hardness increase of the TNMZS alloy in the early stage ageing at 400 °C, and the yield strength improved from 459 MPa to 725 MPa, with elongation 6.9–7.9% after ageing for 10 min. Ageing response acceleration by pre-deformation contributed to the precipitation of coherent ω phase, this would provide a possible way for utilizing transition ω phase to improve strength and ductility in similar series of β titanium alloy.

We investigated the tensile and superelastic behaviors of Ti-35Nb-2Ta-3Zr processed by double-faced friction stir processing that results in a roughly 2 times higher yield strength with an elongation of 37%. The friction stir processed specimens exhibited different superelasticity as loading cycle increased. To assess the strength and deformation of gradient structure, in situ micro compression tests were conducted on stir zone and heat affected zone, revealing higher strength in stir zone and better ductility in heat affected zone. The combination of stir zone and heat affected zone could increase the strength and maintain the ductility of the specimen simultaneously.

Copyright of Rare Metal Materials & Engineering is the property of Northwest Institute for Nonferrous Metal Research and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The flow behavior of metastable β titanium alloy was investigated basing on isothermal hot compression tests performed on Gleeble 3800 thermomechanical simulator at near and above β transus temperatures. The flow stress curves were obtained for deformation temperature range of 800–1100 °C and strain rate range of 0.01–100 s−1. The strain compensated constitutive model was developed using the Arrhenius-type equation. The high correlation coefficient (R) as well as low average absolute relative error (AARE) between the experimental and the calculated data confirmed a high accuracy of the developed model. The dynamic material modeling in combination with the Prasad stability criterion made it possible to generate processing maps for the investigated processing temperature, strain and strain rate ranges. The high material flow stability under investigated deformation conditions was revealed. The microstructural analysis provided additional information regarding the flow behavior and predominant deformation mechanism. It was found that dynamic recovery (DRV) was the main mechanism operating during the deformation of the investigated β titanium alloy.

In the present work, a Ti-40Zr-12Ta (in atom percent, at%) alloy with the spinodal decomposition was designed based on the isothermal section of the Ti-Zr-Ta ternary phase diagram. The alloy was first solid solution treated at 1000 °C and then cold rolled with a thickness reduction of 70% at room temperature. After that, the as-rolled samples were annealed at the temperatures ranging from 500 °C to 900 °C, and the effects of annealed temperature on the microstructure and mechanical properties were investigated. It is found that the spinodal decomposition occurred in the alloy at the temperature ranging from 500 °C to 700 °C, leading to the formation of the periodically distributed Ta-rich (β 1) and Ta-lean phases (β 2). The as-rolled Ti-40Zr-12Ta alloy exhibited a relative high strength due to the work hardening and solid solution strengthening. Annealing treatment at 500 °C promoted the strength of the alloy but significantly decreased its plasticity due to the formation of nano-scale isothermal ω phases. The sample annealed at 700 °C exhibited good tensile mechanical properties, and the modulated structure introduced by spinodal decomposition and TRIP effect contribute to the improvement of its strength and plasticity. • Ti-40Zr-12Ta with the spinodal decomposition was designed according to isothermal section of the phase diagram at 727 °C. • The spinodal decomposition occurred in the alloy during annealing at the temperatures ranging from 500 °C to 700 °C. • Stress-induced martensitic phase transformation occurred in the alloy at 700 °C, which contributed to the plasticity. • The formation of the nanoscale periodically distributed β 1 and β 2 by spinodal decomposition contributed to the strength. [ABSTRACT FROM AUTHOR]

The tensile property and deformation microstructure of a series of metastable β Ti-V-Fe and Ti-V-Fe-Al alloys have been studied. The results show that although Al is an α-stabilizer element, Al addition suppresses the athermal ω phase transformation in metastable β Ti-V-Fe-Al alloys. The Ti-16V-Fe alloy plastically deforms via {332}〈113〉 mechanical twinning and stress-induced ω phase with a special habit plane of {−5052} ω //{3-3-2} β , and the Ti-14V-2Fe-Al and Ti-12V-2Fe-Al alloys via {332}〈113〉 twinning. The Ti-16V-2Fe, Ti-16V-2Fe-Al and Ti-16V-2Fe-2Al alloys with relatively high β phase stability plastically deforms mainly via dislocation glide. The Ti-16V-Fe, Ti-14V-2Fe-Al and Ti-12V-2Fe-Al alloys exhibit higher yield strength without loss of plasticity significantly than the binary β Ti-V alloys deformed via {332}〈113〉 twinning due to solid-solution strengthening effect of Fe and Al elements in the alloys. [ABSTRACT FROM AUTHOR]

The influences of grain size on the deformation behavior of a metastable β-type Ti–12Mo (wt%) alloy has been investigated by using uniaxial tensile testing, scanning electron microscopy and electron backscatter diffraction. The results reveal that the twinning-induced plasticity (TWIP) effect mediated by {332}<113> β twins occurs in this alloy when its mean grain size (d 0) ranges from 49 to 104 µm, leading to pronounced work hardening behavior and a large uniform elongation (> 25%). Furthermore, there is a Hall-Petch relationship between the yield strength and d 0 for this d 0 range, with a Hall-Petch coefficient higher than that expected for pure slip deformation. However, when this alloy is in a state with heterogeneous grain structures and smaller grain sizes (d 0 ∼ 30 µm), only a very limited volume fraction (< 1.8%) of {332}<113> β twins occurs and these twins prefer to nucleate in large grains (> ∼40 µm), but they can propagate into rather small grains (< ∼25 µm). In such a state, the Ti−12Mo alloy has a high yield strength (1025 MPa) but does not exhibit any sign of work hardening, i.e., the TWIP effect is absent. Based on the α " -assisted {332}<113> β twinning mechanism, the effects of grain size on the {332}<113> β twinning and yield strength are discussed in terms of its role in affecting the stress-induced β→α " martensitic transformation. • TWIP effect and pronounced work hardening behavior occur for large β grain sizes. • The introduction of TWIP effect enhances the Hall-Petch coefficient for pure slip. • The decrease of β grain size suppresses the TWIP effect. [ABSTRACT FROM AUTHOR]

The structure and phase composition of β titanium alloy Ti-15V-3Cr-3Al-3Sn-1Zr-1Mo processed by rotary swaging with subsequent aging was studied using the methods of EBSD, scanning and transmission electron microscopy, and X-ray diffraction analysis. It was found that the treatment leads to the decomposition of deformed supersaturated β solid with the precipitation of a lamellar α/α" phase with a volume fraction of up to 20 % and the thickness range from 7 to 35 nm depending on the aging temperature. The study of mechanical properties showed that rotary swaging at 800 °C and subsequent aging at a temperature of 420 °C for 10 h leads to an almost twofold increase in the ultimate strength of the alloy from 800 to 1550 MPa while maintaining satisfactory ductility (∼ 4 %). An increase in the aging temperature to 450 °C leads to a decrease in the strength characteristics of the alloy due to the coagulation of α/α"-phase precipitates and a decrease of internal stresses in the β phase. The results obtained create good prerequisites for the application of the treated alloy, including in aerospace industry. • Rotary swaging with subsequent aging was applied for β titanium alloy for the first time. • The treatment leads to decomposition of β solid with α/α" lamellar varied from 7 to 35 nm. • RS + aging at 420 °C, 10 h leads to an almost twofold increase in alloy ultimate strength. [ABSTRACT FROM AUTHOR]

The microstructure and texture were investigated in cold-rolled Ti-15Mo-3Al-2.7Nb-0.2Si alloy with differing degrees of reduction. The texture of the alloy was prone to rotate to <110> orientation and more sub-boundaries were produced with the increase of the cold-deformation. Precipitation during aging was influenced by the dislocations, sub-boundaries and other defects formed in cold rolling, for they would provide assisted-nucleation sites and decrease the duration of β→α transformation. The α precipitates with the scale of 100–400 nm in the cold-rolled 20% plus aging sample, brought about the high-strength of 1612 MPa and the elongation of 6.5%. The highest strength of 1770 MPa was obtained in the cold-rolled 50% plus aging sample, which has little plastic deformation, due to the coarse α phase precipitated in sub-boundaries. The role of dislocations and sub-boundaries in influencing α precipitation and the tensile properties of Ti-15Mo-3Al-2.7Nb-0.2Si alloy are described in this paper. [ABSTRACT FROM AUTHOR]

The low temperature superplastic deformation behavior of Ti–3.5Al–5Mo–6V–3Cr–2Sn–0.5Fe alloy were investigated. Results show that the elongation of the alloy exceeds 100% when deformation at the temperature ranging from of 650 °C to 800 °C and the initial strain rates ranging from 2.78×10 −4 s −1 to 8.33×10 −3 s −1 , and the elongation of the alloy increases with the decrease of initial strain rates and the increase of temperature. The true strain–stress curves show that the peak flow stress decreases with the decrease of initial strain rates and the increase of temperatures, and the peak flow stress shows much sensitivity to the initial strain rates as well as the temperatures. During superplastic deformation, the α phase was elongated and the size grows up with the decrease of initial strain rates. The superplastic mechanism of the alloy is grain boundary sliding accommodated by dislocation movement and dynamic recrystallization. [ABSTRACT FROM AUTHOR]

Tensile properties and deformation microstructures of a series of binary β Ti–16–22V alloys have been investigated. The results show that the plastic deformation mode changes from the plate-like stress-induced ω phase transformation with a special habit plane of {− 5052} ω //{3 − 3 − 2} β to {332}<113> type deformation twinning with increasing the content of vanadium in the β Ti–16–22 wt.% V alloys. The plate-like stress-induced ω phase has a special orientation relationship with the β phase matrix, i.e., [110] β //[− 12 − 10] ω , (3 − 3 − 2) β //(− 5052) ω and (− 55 − 4) β //(30 − 31) ω . The alloys plastically deformed by stress-induced ω phase transformation exhibit relatively higher yield strength than those deformed via {332}<113> type deformation twinning. It can be concluded that the stability of β phase plays a significant role in plastic deformation mode, i.e., stress-induced ω phase transformation or {332}<113> type deformation twinning, which governs the mechanical property of the β Ti–16–22 wt.% V alloys. [ABSTRACT FROM AUTHOR]

A nanostructured surface layer was successfully performed on a biomedical β-type TiNbZrFe alloy by surface mechanical attrition treatment (SMAT). The results reveal that the surface layer along the depth from treated surface to strain-free matrix could be divided into an outer nanocrystalline layer (0–30 μm), a high-density dislocation region (30–200 μm) and an inner region with low-density dislocations and twins (200–700 μm) when the surface was treated for 60 min. The microhardness of the surface layer is enhanced and increases with increasing treatment time. Although the {1 1 2} 〈1 1 1〉 twin coordinates the deformations with dislocations, this coordination only occurs in the low strain area and cannot affect the nanocrystalline formation. The self-nanocrystallization of TiNbZrFe alloy is mainly attributed to dislocation movements. First, the dislocations start to move and easily form dislocation bands along certain crystal directions; then, multiple slips of dislocations gradually form dislocation tangles; after that, high-density dislocation tangles increases, which divides primary grains into many small domain areas. As high strain energies accumulate on the interfaces among these areas, the lattice rotation can be driven between the adjacent small domain areas, finally resulting in a large number of nanocrystalline regions with low or large angle grain boundaries. [ABSTRACT FROM AUTHOR]

Abstract: The mechanical properties and microstructures of β Ti–25%Nb–11%Sn ternary alloy rods were investigated for biomedical applications as a function of heat treatment temperature after swaging by an 86% reduction in cross-section area. An as-swaged rod consisting of a β (bcc) single phase shows a low Young''s modulus of 53GPa, which is interpreted in terms of both the metastable composition of the β alloy undergoing neither an athermal ω transformation nor a deformation-induced ω transformation and <110>texture development during swaging. Heat treatment at 673K (400°C) for 2h leads to a high strength of approximately 1330MPa and a high spring-back ratio of yield stress to Young''s modulus over 15×10−3, with acceptable elongation. This high strength is attributable to needle-like α precipitates, which are identified by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and high-resolution electron microscopy (HREM). [Copyright &y& Elsevier]

The introduction of severe plastic deformation by high-pressure torsion greatly altered the ageing response of a Ti–20wt.% Mo β alloy, promoting equiaxed (instead of acicular) α precipitation to form a complete ultrafine-duplex (α+β) structure when subjected to sufficiently high strain. Three prominent features, namely abundant grain boundaries, enhanced atomic transport and nanoscale β matrix grains, were recognized as decisive factors contributing to such unusual precipitation behaviour. [ABSTRACT FROM AUTHOR]

Abstract: Severe plastic deformation in the form of equal channel angular pressing (ECAP) has been adopted to introduce severe shear strain into a Ti–20 wt.% Mo β-type titanium alloy to elucidate the aging response of the severely deformed β matrix. Upon isothermal aging in the (α+β) phase field, selective heterogeneous α nucleation and growth resulted in a mixed precipitation microstructure. An ultrafine-duplex (α+β) structure composed of equiaxed α precipitates formed inside the shear bands (SBs) created during ECAP, whereas acicular α precipitates were favoured outside the SBs. This distinct precipitation structure has been correlated to the structural characteristics of the SBs: high disorder with dislocation cells characteristic of low-angle boundaries and enhanced atomic diffusivity. The highly disordered structure results in a weak variant selection and thereby promotes randomly orientated α precipitation without obeying the Burgers orientation relationship. Furthermore, the enhanced atomic diffusivity facilitates rapid growth of the α nuclei to form the ultrafine-duplex (α+β) structure. [Copyright &y& Elsevier]

Abstract: The purpose of this study is to investigate the biocompatibility and osteoconduction of active porous calcium–phosphate films on the novel Ti–3Zr–2Sn–3Mo–25Nb biomedical alloy. The active porous calcium–phosphate films were prepared by the micro-arc oxidation method on the surface of a near β biomedical Ti–3Zr–2Sn–3Mo–25Nb alloy, and then activated in a hydroxyl solution followed by an aminated solution. The phase composition, surface micro-topography and elemental characteristics of the active porous calcium–phosphate films were investigated with XRD, SEM, EDS and XPS. The biocompatibility was assessed using corrosion testing, the in vitro osteoblast cultivation test and implantation in soft tissue (subcutaneous and musculature). The osteoconduction was evaluated using the simulated body fluid test and by implantation in hard tissue. The results show that the active porous films are mainly composed of TiO2 anatase and rutile. The oxide layer is a kind of porous ceramic intermixture containing Ca and P. Immersion in simulated body fluid can induce apatite formation on the porous calcium–phosphate films resulting in excellent bioactivity. Cell cultures revealed that MC3T3-E1 cells grew on the surface exhibiting favorable morphologies. These results indicate that the Ti–3Zr–2Sn–3Mo–25Nb biomedical alloy coated with an active porous calcium–phosphate film has been shown to have excellent corrosion resistance, good biocompatibility and osteoconduction, which can promote cell proliferation and bone formation. [Copyright &y& Elsevier]

Abstract: A novel (TiB+La2O3)/Ti-alloy composite was In situ synthesized through homogeneously melting in a non-consumable vacuum arc remelting furnace. Ti–35Nb–2Ta–3Zr β titanium alloy was chosen as the matrix Ti-alloy and different mass fractions of LaB6 were chosen as additions. Microstructure observations were examined by optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscopy (TEM). The phase analysis was identified by X-ray diffraction (XRD). Largest ultimate tensile strength around 580 MPa and highest elongation around 30% is obtained in 0.1% LaB6-additioned specimen. The appearance of too many La2O3 particles and the reduction of oxygen in the matrix alloy also attribute much to the strength and plasticity of (TiB+La2O3)/Ti composites. Lower ultimate tensile strength around 526 MPa is obtained in 0.5% LaB6-additioned specimen. [Copyright &y& Elsevier]

This work investigated the effect of cooling rate (water quenching and air cooling) on the precipitation of ω phase after solution treatment in β-phase region, and its effect on the mechanical properties in a novel metastable β titanium alloy (Ti–5Mo–3Cr–Fe–3Zr). The initial microstructures, phase composition and deformation-induced microstructures have been investigated using SEM, EBSD, XRD, and TEM. The phase composition of water-quenched alloy and air-cooled alloy are β, α", and ω phase. The size and volume fraction of ω phase of air-cooled alloy are larger than that of water-quenched alloy, resulting in an increase in tensile strength and a decrease in ductility. Deformation mechanisms of Ti–5Mo–3Cr–Fe–3Zr alloy with different cooling rate change from stress-induced ω phase transformation and dislocation slip to only dislocation slip. The stress-induced ω lamellas parallel to [1-11] β direction along the [0001] ω1 direction, which is formed by {112} β <111> β slip. Dislocations can cut through the encountered ω phase to form ω-free deformation bands, which accounts for the ductility. • The size and volume fraction of ω phase of air-cooled alloy are larger than that of water-quenched alloy. • Deformation induced β to ω phase and ω to β phase transformation simultaneously appear in water-quenched alloy. • Dislocations can cut through the encountered ω phase to form ω-free deformation bands, which accounts for the ductility. [ABSTRACT FROM AUTHOR]

Abstract: The present paper is aimed at investigating the behaviour of fatigue cracks emanating from edge-notches for two different microstructures of the Ti-6246 alloy, produced by two specific thermo-mechanical treatments and defined as β-annealed and β-processed, respectively. Pulsating four point bending tests were performed on double-edge-notched specimens. The initiation and early propagation of fatigue cracks were investigated at two relatively high nominal stress levels corresponding to 88 and 58% of the 0.2% material’s yield stress. Plastic deformation at the notch tip initially produced a local stress redistribution followed by elastic shake down due to the high cyclic strain hardening rates exhibited by both microstructures, as confirmed by finite element modelling. Crack closure effects, measured by an extensometric technique, and variations in crack aspect ratio were considered in the ΔK calculation. The obtained crack growth rate data were compared with those of long cracks measured on standard C(T) specimens as well as of microcracks measured on round, unnotched S–N type of specimens to evaluate the intrinsic fatigue crack propagation resistance of the two microstructures. The contribution of notch plasticization to crack closure was estimated by finite element modelling. [Copyright &y& Elsevier]

Abstract: The shape memory effect and superelasticity of Ti-3Zr-2Sn-3Mo-15Nb (TLM) alloy under different conditions of deformations, temperatures, deformation strains and heat treatments were studied by bending and tensile tests. The results indicate that TLM alloy specimens hot rolled or cooled from α+β dual phase region have higher shape recovery ratio than that cooled from β single phase region, whose maximum completely recovery strain reaches 1.8%. The shape recovery ratio decreases with the increase of the total deformation strain, which has been proved in many other beta titanium alloys. The TLM alloy specimen cooled from β single-phase region in air exhibits the best superelasticity compared with that of hot rolled or aged specimens. [Copyright &y& Elsevier]

Abstract: Metastable β titanium alloy Ti–10V–2Fe–3Al is known to exhibit a shape memory effect due to a stress-induced α″ martensitic transformation at room temperature. In the present study, nitrogen (N) was added to this alloy to strengthen the β matrix. The effect on the deformation behavior of β phase was studied. Thermally induced martensite is formed in the N-free alloy by quenching after β solutionizing but it is not observed in the alloys containing nitrogen of more than 0.1mass%. Superelasticity due to stress-induced formation of α″ martensite was observed in the 0.1 and 0.2N alloys. N addition is moreover effective in increasing a true elastic strain up to 1% by strengthening of the β matrix. [Copyright &y& Elsevier]

TIMETAL LCB was introduced more than 10 years ago targeting automotive suspension spring applications. The alloy development aim was to use a low-cost formulation by selecting less expensive raw materials than typical beta titanium alloys. Following the first successful application of TIMETAL LCB suspension springs to series production vehicles, the 2000 Volkswagen Lupo FSI, the springs have been used for Ferrari Challenge Stradale since 2003. The most recent development effort was focused on the generation of metallurgical and mechanical service data for the alloy, and the implementation of efficient low cost processing of coils. This paper will introduce various properties of TIMETAL LCB products that can be useful in the design and the consideration of spring applications. Recent progress in the processing of TIMETAL LCB will also be introduced and discussed. [ABSTRACT FROM AUTHOR]

Deformation behavior at room temperature was examined in near-β titanium alloys, Ti-10V-2Fe-3Al, containing small amounts of N up to 0.2 mass%. After a β solution treatment, thermally induced α″ martensite is formed in the N-free alloy but no martensite is formed in the 0.1 and 0.2% N alloys. In the N-free alloy, stress-induced α″ martensite transformation occurs during deformation at room temperature, and a shape memory effect by heating after deformation is exhibited, as was previously reported. In the N-containing alloys, shape recovery over 90%, which is much larger than that in the N-free alloy, was obtained by unloading after a bending deformation. In the 0.1% N alloy, forward and reverse martensite transformations are observed during tensile deformation by in-situ optical microscopy, confirming the occurrence of superelasticity in this alloy. On the other hand, a large elastic strain over 1% is obtained in the 0.2% alloy by strengthening of β matrix, although the α″ martensite introduced by further deformation does not disappear by unloading. [ABSTRACT FROM AUTHOR]

Beta titanium alloys are increasingly the best choice for automotive and aerospace applications due to their high performance-to-density ratio. Among these alloys, the TIMETAL Ti-LCB is already used in the automotive industry because it presents excellent mechanical properties and a lower cost compared with other Ti alloys. The current study deals with the characterization of the nucleation and growth of the α phase in several thermomechanical processes, because the distribution and size of the α phase strongly influence the mechanical properties of the resulting microstructures. Several heat treatments were conducted after either cold rolling or annealing. The resulting microstructures were characterized by scanning electron microscopy, transmission electron microscopy, x-ray diffraction, or electron backscatter diffraction. It was observed that the morphology and the volume fraction of the α phase are strongly dependent on the holding temperature, on the heating or cooling rate, and on the β grain size. [ABSTRACT FROM AUTHOR]

• Radial shear and groove rolling allow to obtained strength wire of β titanium alloy. • Ultimate strength of the wire is 1320 MPa with maintaining good ductility (6%). • Fracture analyzes revealed the development of ductile tensile rapture of the wire. In the paper the effect of strain during rolling on the structure, mechanical properties and fracture of the Ti-15 V-3Al-3Sn-3Cr-1Mo-1Zr alloy in the process of wire obtaining has been studied. It is shown that at the strain value e = 6.3 the processing leads to the formation in the alloy of stripe fragmented structure with thickness of 50–100 nm. As a result, the wire of the β titanium alloy with high ultimate strength (1320 MPa) and satisfactory ductility (6%) was obtained. The resulting wire also demonstrates ductile fracture after tension at room temperature. [ABSTRACT FROM AUTHOR]

• Combined rolling with aging results in hierarchical structure in β titanium alloy. • Ultimate strength of alloy after CR and aging double increased with good ductility. • Fatigue properties of CR and aged alloy increases at amplitudes above 500 MPa. In the paper the effect of radial-shear and groove rolling with subsequent aging on the structure, mechanical and fatigue properties of the Ti-15V-3Al-3Sn-3Cr-1Mo-1Zr alloy has been studied. It is shown that the specified processing leads to the formation in the alloy of a homogeneous hierarchical structure with lamellar precipitates of the α″-phase 20–30 nm thick in the volume of grains of the β phase with an average size of 10 μm. As a result, it is more than double increase in ultimate strength of the alloy (from 800 to 1630 MPa) while maintaining satisfactory plasticity (5.3%) It was found that such treatment also significantly increases the resistance to the development of fatigue fracture of the alloy at stress amplitudes above 500 MPa. [ABSTRACT FROM AUTHOR]

The influence of laser offsets on the composition, microstructure, and tensile properties of laser welded Ti-3Al-6Mo-2Fe-2Zr and TA15 dissimilar joints was investigated. Laser offsets of −0.1 mm, 0 mm, and 0.1 mm were adopted for the welding process with laser beam shifting from Ti-3Al-6Mo-2Fe-2Zr to centerline and TA15, respectively. The microstructure evolution in the HAZ was extensively discussed using numerical simulation. In the HAZ of Ti-3Al-6Mo-2Fe-2Zr alloy, a single-β-phase region was formed because both the α p and α s phase had transformed into β phase on heating, and the following β → α p , α s transformation was suppressed by the fast cooling rate and high content of β-stabilizing elements. The α → β transformation also occurred on heating in the HAZ of TA15 alloy, followed by the β → α' transformation during the cooling period. For different laser offsets, the microstructure of fusion zone was composed of columnar β phase and α' martensites. The α' martensites were dispersed inhomogeneously in the different regions of fusion zone. The region closest to TA15 alloy presented larger amount and size of α' martensites than the regions closest to Ti-3Al-6Mo-2Fe-2Zr. As the laser offset changed from −0.1 mm to 0.1 mm, the amount and size of α' martensites increased as a result of higher [Al] eq and lower [Mo] eq. The joints with laser offsets of −0.1 mm and 0 mm fractured in the tensile deformation stage. The joints with laser offset of 0.1 mm exhibited the highest strength and plastic deformation capacity because of the strengthening effects of α' martensites. [Display omitted] • The β → α transformation is suppressed by the high [Mo] eq and fast cooling rate. • α' martensites are disperse inhomogeneously across the fusion zone. • The amount and size of α' martensites increase as laser offset rises to 0.1 mm. • The joints produced with laser offset of 0.1 mm exhibit the best performance. [ABSTRACT FROM AUTHOR]