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Ti-29Nb-13Ta-4.6Zr (TNTZ) is a new titanium alloy potentially to be used as bone implant material because of its advantages in terms of strength, ductility, non-toxicity, corrosion resistance, and biocompatibility. Its mechanical properties are suitable for bone applications; however, there are still problems related to its corrosion behavior when used for a long time. Therefore, this research aims to determine the corrosion rate and types, and provide corrosion prevention by applying the thermomechanical treatment on TNTZ in Hanks’ solution. The limitation of this research was in not conducting the TNTZ biocompatibility tests. This research was conducted using the potentiodynamic polarization method in Hanks’ solution as the corrosive medium at a temperature of 37°C and a pH of 6.8. Before corrosion testing, a TNTZ sample was treated with thermomechanical treatment combined with solution treatment at a temperature of 850°C and a holding time of 45 minutes, followed by rapid cooling (water quenching), and plastic deformation with deformation variations of 10%, 15%, and 20%, and it was ended with aging heat treatment at a temperature of 300°C and holding time for 1 hour. The novelties of this research are the valid data of corrosion rate and type of TNTZ, which were unavailable before, and corrosion prevention through thermomechanical treatment of TNTZ in Hanks’ solution. The thermomechanical treatment is proved to reduce the pitting corrosion in TNTZ. The results show that thermomechanical treatment and increased plastic deformation can reduce the value of the corrosion rate, as evidenced by the pre-thermomechanical and thermomechanical TNTZ corrosion rates with deformation variations of 10%, 15%, and 20%, respectively, which were 5.522 x 10-4 mmpy; 2.754 x 10-4 mmpy; 2.290 x 10-4 mmpy; and 2.064 x 10-4 mmpy, respectively. TNTZ, after thermomechanical treatment, had the lowest corrosion rate, i.e., 2.064 x 10-4 mmpy, while Ti-6Al-7Nb had the highest one, i.e., 3.05 x10-2 mmpy. The type of TNTZ corrosion is pitting corrosion, as shown by the loss of zirconium that reduced the volume, causing pits to occur. Meanwhile, after thermomechanical treatment, pitting corrosion happened on TNTZ because of the loss or release of zirconium. This research shows that after thermomechanical treatment, TNTZ is the best material compared to other materials for biomedical applications based on corrosion resistance.

Thermal oxidation is one of the simple and low-cost methods that can improve tribological characteristics of titanium and its alloys by generating a protective layer on their surfaces. In this study, the experiment parameters were applied on thermal oxidation (TO) at 598, 673 and 723K for 40, 50 and 60s on TNTZ. The micro-Vickers hardness tests and microstructure analysis were performed for specimens before and after TO. The results exhibited that the hardness of TNTZ was increased by increasing TO temperature, but it was decreased by enlarging of TO time. Metallographic tests showed that oxidised TNTZ have equaxial β grains with a grain size approximately about 20-30μm. No significant change of microstructure (grain size) was detected after increasing TO temperature because the short time oxidation process was applied.

Li Q., Song S., Li J., et al. Antibacterial Properties and Biocompatibility of Hydroxyapatite Coating Doped with Various Cu Contents on Titanium. Materials Transactions 63, 1072 (2022); https://doi.org/10.2320/matertrans.MT-M2021245., To explore the effect of copper content in a copper-doped hydroxyapatite coating (CuHAp) on its antibacterial activity and biocompatibility, a layer of CuHAp was deposited on the surface of pure Ti using an electrochemical deposition method. An orthogonal experiment was used to determine the Cu content in the coating by varying the concentration of Cu2+ in the electrolyte. The antibacterial properties and biocompatibility of the CuHAp coatings were also evaluated. The antibacterial effect increased with increasing Cu content in the sample. When the content of Cu in the coating was 1.57%, the deposited CuHAp coating exhibited excellent biocompatibility, and the number of living cells after culturing was significantly higher than that for the HAp coating. When the content of Cu increased to 6.85%, the coating exhibited cytotoxicity. Thus, the CuHAp sample with a Cu content of 1.57% exhibited good antibacterial and biocompatibility, and thus could be a suitable material for use in biomedical applications.

LI Q., HUANG Q., LI J.j., et al. Microstructure and mechanical properties of Ti–Nb–Fe–Zr alloys with high strength and low elastic modulus. Transactions of Nonferrous Metals Society of China, 32, 2, 503. https://doi.org/10.1016/S1003-6326(22)65811-4., Zr was added to Ti–Nb–Fe alloys to develop low elastic modulus and high strength β-Ti alloys for biomedical applications. Ingots of Ti–12Nb–2Fe–(2, 4, 6, 8, 10)Zr (at.%) were prepared by arc melting and then subjected to homogenization, cold rolling, and solution treatments. The phases and microstructures of the alloys were analyzed by optical microscopy, X-ray diffraction, and transmission electron microscopy. The mechanical properties were measured by tensile tests. The results indicate that Zr and Fe cause a remarkable solid-solution strengthening effect on the alloys; thus, all the alloys show yield and ultimate tensile strengths higher than 510 MPa and 730 MPa, respectively. Zr plays a weak role in the deformation mechanism. Further, twinning occurs in all the deformed alloys and is beneficial to both strength and plasticity. Ti–12Nb–2Fe–(8, 10)Zr alloys with metastable β phases show low elastic modulus, high tensile strength, and good plasticity and are suitable candidate materials for biomedical implants.

Li Q., Yang J., Li J., et al. Antibacterial Cu-doped calcium phosphate coating on pure titanium. Materials Transactions 62, 1052 (2021); https://doi.org/10.2320/matertrans.MT-M2021005., Cu-doped amorphous calcium phosphate (ACP) coatings were fabricated on the surface of pure titanium (Ti) by electrochemical deposition at initial electrolyte temperatures of 35, 45, and 55°C. The antibacterial activities of the coatings were then evaluated by the plate counting method using Escherichia coli as the indicator. The Cu concentrations on the surfaces of samples are increased from 6.90 to 15.05 mass% as initial electrolyte temperature is increased from 35 to 55°C. The Cu-doped ACP coatings show that they can fully inhibit the growth of E. coli.

Hydroxyapatite (HA) coating has been carried out on a titanium alloy Ti–29Nb–13Ta-4.6Zr (TNTZ) to improve the biocompatibility and bioactivity of the alloy in order to attain a high degree of osseointegration and low inflammatory reactions in bone tissue after implantation in orthopedic implant applications. The coating process was carried out using the electrophoretic deposition (EPD) method. TNTZ implants with and without HA coating were installed in the tibia of the Rattus norvegicus Wistar test rats; the test animals were then terminated after two weeks. The degree of osseointegration was measured using a removal torque tester, the Tumor Necrosis Factor-Alpha (TNF-α) level was measured by using the Enzyme-Linked Immunosorbent Assay (ELISA) method, and a histopathological analysis was carried out on the implanted tissue. TNTZ implants with HA coating exhibit significantly higher osseointegration compared to those without HA coating, whereas TNTZ implants without HA coating can trigger significantly higher TNF-α levels. Greater osteogenesis occurs in a bone tissue fitted with TNTZ implants with HA layers. The HA coating on the surface of the TNTZ implant can reduce excessive inflammation, enhance the osteogenesis process, and then improve osseointegration in the bone tissues of test animals. It is also expected to be suitable for orthopedic implant applications.

Ti-15Nb-25Zr-(0, 4, 8)Fe (mol.%) alloys were prepared via spark plasma sintering (SPS) for 10 min at 800, 1000, and 1200 °C to study the effect of sintering temperatures and Fe content on the mechanical properties of alloys. The main phase of the alloys sintered at 800 °C is α phase. When the temperature is increased to 1000 and 1200 °C, the alloys are mainly β phase. Raising the sintering temperature can promote the diffusion of elements. Therefore, high strength and high plasticity are obtained in the alloys sintered at high temperature. The compressive strength of Ti-15Nb-25Zr sintered at 1200 °C is 1604 MPa, and the fracture strain is around 35%. The strength and plasticity are influenced by the complex effects of elemental diffusion, grain boundary and solid-solution strengthening. Adding Fe can improve the diffusion of elements, promote the formation of β grains and supply solid-solution strengthening effect. As the sintering temperature is increased, the compressive strength of Ti-15Nb-25Zr-4Fe shows an increasing trend and the plasticity is almost not changed. The Fe content is excessive in Ti-15Nb-25Zr-8Fe, which leads to some disadvantages including intermetallic compounds formation and grain boundary coarsening. The mechanical properties of Ti-15Nb-25Zr-8Fe are not always better than those of Ti-15Nb-25Zr-4Fe. The compressive strength of Ti-15Nb-25Zr-8Fe shows an increasing trend and the plasticity firstly increases and then decreases when the temperature is raised from 800 up to 1200 °C. Although the sintering time of SPS is short, Ti-15Nb-25Zr-(4, 8)Fe sintered at 1000 °C and Ti-15Nb-25Zr-(0, 4)Fe sintered at 1200 °C show good combination of strength and plasticity.

The development of new low-cost alloys composed of common elements that show high biocompatibility and mechanical properties matching with human bone is the target of many researches recently. Design and controlling the mechanical properties of newly developed set of Ti-xFe-3Zr-yNb (x=3-8 & y=2-3, at.%) low-cost alloys through applying different thermomechanical treatments is the aim of this work. Fe-content in the present designed alloys is changing in the range 3 to 8 at.%. The hardness and Young's modulus of the alloys were measured for the alloys in the solution treated, hot rolled and subsequent ageing at 400 °C and 550 °C. The phases separation and hence hardness of the aged alloys at 400 °C and 550 °C are highly dependent on the Fe-content in the alloy. The Young's modulus of the alloys is also changing with the Fe-content and heat treatment, where lowest modulus (~80GPa) is shown in the Ti-5Fe-3Zr-3Nb alloy in the solution treated condition.

A series of Ti-(38-2x)Nb-xMo (wt.%) alloys are designed using 1% Mo to replace 2% Nb in order to gradually increase the β stability and obtain a low springback. The α″ phase is exhibited in Ti-38Nb and suppressed with an increasing Mo content. The Ti-38Nb and Ti-34Nb-2Mo alloys show stress-induced α″ martensite transformations during cold rolling and double yielding behavior in tensile tests. The Ti-30Nb-4Mo and Ti-26Nb-6Mo alloys exhibit nonlinear deformation owing to the metastable β phase. With an increase in the Mo content, Young’s modulus increases slightly from 68 GPa in Ti-38Nb to 73 GPa in Ti-26Nb-6Mo, owing to the increase in β stability. Mo shows a solution strengthening effect that gradually increases the tensile strength. Although a higher Young’s modulus was not observed to be induced through deformation in Ti-(38-2x)Nb-xMo alloys, low springback was obtained according to the three-point bending loading–unloading test. In particular, the Ti-38Nb and Ti-34Nb-2Mo alloys with stress-induced α″ martensite transformations exhibit low yielding stress and are thus easily deformed. The deformed α″ phase hardly reverts to the β matrix after unloading, and therefore, the plastic deformation is maintained.

A series of Ti-29Nb-(4, 7, 10, 13)Zr-2Cr alloys were fabricated to investigate the influence of Zr content on microstructures and mechanical properties. All the four alloys present a single β phase after solution treatment. With the increase in Zr content, the 0.2% proof stress is gradually increased from 388 MPa in Ti-29Nb-4Zr-2Cr to 713 MPa in Ti-29Nb-13Zr-2Cr. The Young’s modulus gradually is decreased from 80 GPa in Ti-29Nb-4Zr-2Cr to 63 GPa in Ti-29Nb-13Zr-2Cr. The elongation shows the same trend as that of Young’s modulus. The changes of mechanical properties are influenced by the β stability and solid solution strengthening effect, which are both enhanced by Zr addition. The Ti-29Nb-13Zr-2Cr alloy presents a Young’s modulus of 63 GPa, tensile strength of 730 MPa and elongation of 18% and is a promising biomedical material.

In the present study, we evaluated the effects of high pressure torsion (HPT) and subsequent short time annealing processing on fatigue properties and cytocompatibility of the biomedical Co–Cr–Mo alloy (CCM). Before processing, CCM was solution treated (CCMST) to achieve a microstructure composed of coarse single γ-phase equiaxed grains with no internal strain. Through HPT processing, an inhomogeneous microstructure containing both micro- and nano-scaled grains is obtained in CCM specimens, which were named as CCMHPT, accompanied by high internal strain and extensive ε martensite. Following a subsequent short time annealing, a uniform single γ-phase ultrafine-grained microstructure with small local strain fields dispersed forms in CCM specimens, which were named as CCMHPTA. This microstructure change improves fatigue strength in CCMHPT, and further in CCMHPTA, because of the enhanced crack initiation and/or propagation resistance. For cytocompatibility evaluation, the cells cultured on CCMST show an immobilization tendency, while those cultured on CCMHPT exhibit a locomotion tendency. The cells cultured on CCMHPTA have an intermediate pattern. Compared with CCMST, much larger numbers of cells are proliferated in both CCMHPT and CCMHPTA. All these results demonstrate that the CCMHPTA offers an improved fatigue property and a good cytocompatibility. Therefore, it is promising for use in biomedical applications.

In this study, the TiO2-matrix coatings including hydroxyapatite (HA) and tricalcium phosphate (TCP) were successfully deposited on the β-type Ti–29Nb–13Ta–4.6Zr alloys by plasma electrolytic oxidation (PEO) process to enhance the in-vitro corrosion resistance of the alloys. An electrolyte containing calcium hydroxide (CaOH) and sodium phosphate dodecahydrate (Na3PO4·12H2O) were used to prepare micro-arc oxidized samples. The effect of duty cycle, deposition frequency, coating thickness, and surface morphologies have been discussed in the view of corrosion phenomena. The coated morphologies were characterized with scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS). The corrosion behaviors of the coatings were investigated using potentiodynamic polarization scanning (PDS) technique in Ringer's solutions at body temperature. In addition, the immersion tests on the coated and uncoated samples were performed to observe the apatite phase formation on the surface. X-ray diffraction technique (XRD) has been used in order to determination Ca- and P-based phases on the surfaces. It was found that the corrosion rates of the all coated samples were approximately 4–14 times lower than the uncoated TNTZ sample. The highest resistant coating to corrosion was obtained in the oxidized TNTZ samples deposited at 500 Hz with 30% duty cycle by PEO.

Li Q., Qi Q., Li J., et al. Low springback and low Young’s modulus in Ti-29-Nb-13Ta-4.6Zr alloy modified by Mo addition. Materials Transactions 60, 1755 (2019); https://doi.org/10.2320/matertrans.ME201912., Deformation-induced higher Young’s modulus can satisfy the contradictory requirements of Ti alloys for spinal-fixation applications, which demand a high Young’s modulus to reduce springback during operations and a low Young’s modulus to prevent stress shielding effect for patients after surgeries. In this study, TNTZ-(1, 3, 5)Mo are designed by adding Mo and Ti to Ti-29-Nb-13Ta-4.6Zr (TNTZ) in order to maintain low initial Young’s modulus and achieve low springback. All the solutionized alloys show single β phase with increasing the β stability by Mo addition. They show low Young’s moduli less than 65 GPa, similar ultimate tensile strength of 650 MPa and elongation around 20%. The springback of TNTZ-3Mo and TNTZ-5Mo is lower than that of TNTZ and TNTZ-1Mo owing to their more stable β phase. After cold rolling, TNTZ-3Mo shows the largest increasing ratio of 25% in Young’s modulus and the highest ultimate tensile strength owning to the appearance of deformation-induced ω phase. With the low initial Young’s modulus of 59 GPa, TNTZ-3Mo is a potential candidate to make the spinal rods in spinal fixation devices.

β-Type Ti-Nb-based alloys exhibit satisfactory biocompatibility and low Young’s modulus for biomedical applications. The microstructure and mechanical properties of a series of Ti-(14, 16, 18, 20, 22, 24)Nb-2Fe alloys fabricated by arc melting were investigated by XRD, optical microscopy, and tensile tests. Both ω and α″ phases existed in the Ti-14Nb-2Fe alloy, while just a single β phase existed in the other alloys. Twinning is an important deformation mechanism that causes work hardening and twinning-induced plasticity. It was found in the Ti-(14, 16, 18, 20)Nb-2Fe alloys and not in the Ti-22Nb-2Fe alloy. The Ti-14Nb-2Fe alloy exhibited the highest tensile strength and the highest Young’s modulus owing to the existence of the ω phase. The tensile strength decreased gradually from 830 MPa (highest) for the Ti-14Nb-2Fe alloy to 540 MPa (lowest) for the Ti-24Nb-2Fe alloy with an increase in the Nb content. The Young’s modulus decreased from 90 GPa for the Ti-14Nb-2Fe alloy to 63 GPa for the Ti-22Nb-2Fe alloy and then increased to 71 GPa for the Ti-24Nb-2Fe alloy. Elongation shows the same trend as the Young’s modulus. The Ti-22Nb-2Fe alloy, with a low Young’s modulus of 63 GPa, tensile strength of 570 MPa, and 15% elongation, was found suitable for biomedical applications. The Ti-20Nb-2Fe alloy also exhibits a high tensile strength, a Young’s modulus ratio of 9.24 × 10−3, and 18% elongation and is thus considered another valuable Ti alloy for biomedical applications.

Li Q., Yuan X., Li J., et al. Effects of Fe on microstructures and mechanical properties of Ti-15Nb-25Zr-(0, 2, 4, 8)Fe alloys prepared by spark plasma sintering. Materials Transactions 60, 1763 (2019); https://doi.org/10.2320/matertrans.ME201913., Biomedical Ti-15Nb-25Zr-(0, 2, 4, 8)Fe (mol%) alloys are prepared by mixing pure element powders and spark plasma sintering (SPS). Specimens with diameters of 20 mm and thicknesses of 3 mm are obtained by sintering at 1000°C for 10 min followed by cooling in the furnace. Some of the specimens are then heat-treated at 900°C for 1 h followed by water quenching. Zr and Fe are dissolved in Ti; however, segregation of Nb is observed in all of the alloys. The β and α′′ phases are observed in the as-sintered and heat-treated specimens owing to the insufficient diffusion of the alloying elements. Fe stabilizes the β phase and provides a solution-strengthening effect. With the increase in the Fe content in the as-sintered specimen, the compressive strength and micro-Vickers hardness are improved in the Ti-15-Nb-25Zr-(0, 2, 4)Fe alloys and slightly decreased in Ti-15-Nb-25Zr-8Fe. The as-sintered Ti-15Nb-25Zr-4Fe alloy exhibits the maximum compressive strength of 1740 MPa. Although the plasticity is decreased by the Fe addition, a fracture strain of approximately 17% is obtained for Ti-15Nb-25Zr-4Fe, indicating a good plasticity. The heat treatment cannot eliminate the segregation of Nb, but can improve the plasticity and slightly increase the strengths of Ti-15Nb-25-Zr(0, 2, 4)Fe. Moreover, the heat-treated Ti-15Nb-25Zr-8Fe exhibits a high strength of approximately 1780 MPa and fracture strain of approximately 19%. Therefore, good comprehensive mechanical properties, including high strengths, high hardnesses, and good plasticities, can be obtained in Fe-added β-Ti alloys prepared by SPS and subsequent optional short heat treatment.

Niinomi M., Akahori T., Nakai M., et al. Quantitative and qualitative relationship between microstructural factors and fatigue lives under load- And strain-controlled conditions of Ti-5Al-2Sn-2Zr-4Cr-4Mo (Ti-17) fabricated using a 1500-ton forging simulator. Materials Transactions 60, 1740 (2019); https://doi.org/10.2320/matertrans.ME201904., The fatigue lives of forged Ti-17 using a 1500-ton forging simulator subjected to different solution treatments and a common aging treatment were evaluated under both load- and strain-controlled conditions: high and low cycle fatigue lives, respectively. Then, the tensile properties and microstructures were also examined. Finally, the relationships among fatigue lives and the microstructural factors and tensile properties were examined. The microstructure after solution treatment at 1203 K, which is more than the β transus temperature, and aging treatment exhibits equiaxed prior β grains composed of fine acicular ¡. On the other hand, the microstructures after solution treatment at temperatures of 1063, 1123, and 1143 K, which are less than the β transus temperature, and aging treatment exhibit elongated prior β grains composed of two different microstructural feature regions, which are acicular α and fine spheroidal α phase regions. The 0.2% proof stress, σ₀.₂, and tensile strength, σB, increase with increasing solution treatment temperature up to 1143 K within the (α + β) region, but decrease with further increasing solution treatment temperature to 1203 K within the β region. The elongation (EL) and reduction of area (RA) decrease with increasing solution treatment temperature, and it becomes nearly 0% corresponding to a solution treatment temperature of 1203 K. The high cycle fatigue limit increases with increasing solution treatment temperature up to 1143 K, corresponding to the (α + β) region. However, it decreases with further increase in the solution treatment temperature to 1203 K in the β region. The fatigue ratio in high cycle fatigue life region is increasing with decreasing solution treatment temperature, namely increasing the volume fraction of the primary α phase, and it relates well qualitatively with the volume fraction of the primary α phase when the solution treatment temperature is less than the β transus temperature. The low cycle fatigue life increases with decreasing solution treatment temperature, namely increasing the volume fraction of the primary α phase. The low cycle fatigue life relates well quantitatively with the tensile true strain at breaking of the specimen and the volume fraction of the primary α phase for each total strain range of low cycle fatigue testing.

Invar non-ferromagnetic Ti-alloys with zero thermal expansion coefficients are designed by optimizing both the alloy composition and the thermomechanical treatment. The thermal expansion coefficient is controlled in those alloys which exhibit high elastic softening, since unique microstructures tend to be formed in them by cold deformation. The strains and stresses stored in the alloys by cold deformation are released to some extent in the course of the subsequent heating treatment, which leads to either a negative, positive or zero thermal expansion coefficient, depending on the conditions of cold deformation and heat treatment. Such unique thermal expansion behavior is fully reversible in a certain temperature range.

Different amounts of Cr were added to a metastable β-type Ti–22Nb (at.%) alloy to obtain desirable mechanical properties, including a low Young’s modulus, high strength, and good plasticity. The mechanical properties and microstructural changes were investigated. Cr has a high ability to stabilize the β phase, as well as suppress both α″ martensite and ω phase transformations during quenching and the stress-induced α″ martensite transformation during tension. Solid solution strengthening is scarcely achieved by Cr addition. The changes in mechanical properties can be attributed to the different β stabilities. The Ti–22Nb–(0,1)Cr alloys have metastable β phases and exhibit double yielding phenomena, indicating a stress-induced α″ martensite transformation. The Ti–22Nb–(2,3)Cr alloys with stable β phases exhibit distinct work hardening caused by a {332}β β twinning, which also occurs in the Ti–22Nb–(0,1)Cr alloys, but not in the Ti–22Nb–4Cr alloy. Low Young’s moduli of approximately 60 GPa are obtained for the Ti–22Nb–(1,2)Cr alloys. The Ti–22Nb–2Cr alloy exhibits desirable properties for biomedical applications, including an ultimate tensile strength of approximately 600 MPa and elongation of approximately 20%.

Friction stir welding (FSW) was applied to a butt joint between the 2-mm-thick plates of an (α+β)-type titanium alloy with high hot workability, Ti-4.5Al-2.5Cr-1.2Fe-0.1C alloy (Ti531C), to obtain defect-free welds. Refined equiaxed grains (equiaxed structure) were obtained and anisotropic mechanical properties of the parent material disappeared by grain subdivision of the α phase during FSW. However, grain diameter and crystal texture of the equiaxed structure remained unchanged during annealing. The tensile strengths of the welded joints with and without annealing were comparable to that of the Ti531C parent plate. However, the elongations of the welded joints were lower than that of the Ti531C parent plate because the stir zones are harder than the base metal, which results in deformation preferentially in the base metal region of the specimens. Tensile testing caused a failure in the base metal region in all welded joints. Annealing improved the high-cycle fatigue strength of the welded joints greatly. However, the high-cycle fatigue strength of the welded joints subjected to annealing was still slightly lower than that of the Ti531C parent plate. Fatigue failure point was in the stir zone or at the boundary between the stir zone and the base metal, which are different from the tensile test. These results imply that failure factors are different between tensile and fatigue tests. The small portion of the isothermal ω phase in the β phase in the stir zone and discontinuous microstructure at the boundary between the stir zone and the base metal were potential stress concentration sites, inducing high-cycle fatigue failure.

Silver alloy is one of semi-precious alloys for dental prosthesis, which has been applied remarkably in Japanese dental field. Ag-20Pd-17.7Cu-12Au alloy (G12), which was newly developed for commercial dental silver alloy, shows the unique hardening mechanism after a simple solution treatment (ST) at relatively high temperature. However, the relationship between ST at various temperature and the mechanical strength of G12 has not been investigated fully. Therefore, the relationship between ST and mechanical properties of G12 after ST at various temperatures was investigated systematically in this study. G12 subjected to ST at relatively high temperature of 1173 K is composed of three kinds of phases with Ag-rich α2 phase, Cu-rich α1 phase and β phase of Pd-Cu intermetallic compound. Although nominal melting point of G12 was around 1233 K, the high Cu concentration area like α1 phase was partially dissolved and then the α1, α2 and partial β phases re-precipitated during cooling. On the other hand, the microstructure of G12 aged at 673 K after ST at 1023 K (STA) was mainly composed of two kinds of phases with α2 and α1 phases with a small amount of β phase, which was a typical microstructure of STA. The Vickers hardness of G12 subjected to ST at 1173 K was identical to that of the same alloy subjected to STA although the tensile strength, fatigue limit and ductility deteriorated to some degrees. The corrosion potential of G12 changed drastically with the temperature of ST. The potential may have been increased by the decrease in the volume fraction of the α1 phase with relatively high Cu content.

Oxygen is considered to be an impurity in titanium and its alloys, and it enhances their brittleness. However, oxygen has also been recognized as a useful ingredient to improve the mechanical performance of titanium alloys for biomedical applications, because oxygen is a lightweight interstitial element that is non-toxic and non-allergenic. Some reports show that adding oxygen improves both the strength and the ductility of titanium alloys for biomedical applications. The effects of oxygen addition on the mechanical performance of titanium alloys for biomedical aplications are described.

Co–Cr–Mo alloys are particularly advantageous for use in long-wear implants such as artificial joints and in the cups and heads of artificial hip joints. Co–Cr–Mo alloys are also receiving attention in relation to use in the stents and rods of spinal fixation devices. This chapter discusses the types of Co–Cr–Mo alloys, Ni- and C-free Co–Cr–Mo alloys with the addition of nitrogen, and their mechanical properties, fatigue, corrosion characteristics, biocompatibility, wear properties, and additive manufacturing in the field of biomedical applications.

The microstructures, tensile properties, and fatigue lives of the forged Ti-17 using a 1500-ton forging simulator subjected to different solution treatments and a common aging treatment under both load- and strain-controlled conditions to evaluate high cycle fatigue and low cycle fatigue lives, respectively were examined. Then, the tensile properties, microstructures, and relationships between fatigue lives and the microstructural factors were discussed. The fatigue limit under load-controlled conditions increases with increasing solution treatment temperature up to 1143 K, which is in the (α + β) region. However, it decreases with further increase in the solution treatment temperature to 1203 K in the b region. The fatigue ratio at fatigue limit is increasing with decreasing solution treatment temperature, namely increasing the volume fraction of the primary α phase, and it relates well qualitatively with the volume fraction of the primary α phase when the solution treatment temperature is less than the b transus temperature. The fatigue life under strain-controlled conditions to evaluate the low cycle fatigue life increases with decreasing solution treatment temperature, namely increasing the volume fraction of the primary α phase. The fatigue life under strain-controlled conditions to evaluate the low cycle fatigue life relates well quantitatively with the tensile true strain at breaking of the specimen and the volume fraction of the primary α phase for each total strain range.

Poor kinetics of hole transportation at the electrode/electrolyte interface is regarded as a primary cause for the mediocre performance of n-type TiO2 photoelectrodes. By adopting nanotubes as the electrode backbone, light absorption and carrier collection can be spatially decoupled, allowing n-type TiO2, with its short hole diffusion length, to maximize the use of the available photoexcited charge carriers during operation in photoelectrochemical (PEC) water splitting. Here, we presented a delicate electrochemical anodization process for the preparation of quaternary Ti–Nb–Ta–Zr–O mixed-oxide (denoted as TNTZO) nanotube arrays and demonstrated their utility in PEC water splitting. The charge-transfer dynamics for the electrodes was investigated using time-resolved photoluminescence, electrochemical impedance spectroscopy, and the decay of open-circuit voltage analysis. Data reveal that the superior photoactivity of TNTZO over pristine TiO2 originated from the introduction of Nd, Ta, and Zr elements, whic...