Effects of molybdenum content on the structure and mechanical properties of as-cast Ti-10Zr-based alloys for biomedical applications

The effects of molybdenum on the structure and mechanical properties of a Ti-10Zr-based system were studied with an emphasis on improving the strength/modulus ratio. Commercially pure titanium (c.p. Ti) was used as a control. As-cast Ti-10Zr and a series of Ti-10Zr-xMo (x = 1, 3, 5, 7.5, 10, 12.5, 15, 17.5 and 20 wt.%) alloys prepared using a commercial arc-melting vacuum pressure casting system were investigated. X-ray diffraction (XRD) for phase analysis was conducted with a diffractometer. Three-point bending tests were performed to evaluate the mechanical properties of all specimens. The experimental results indicated that these alloys had different structures and mechanical properties when various amounts of Mo were added. The as-cast Ti-10Zr has a hexagonal α′ phase, and when 1 wt.% Mo was introduced into the Ti-10Zr alloy, the structure remained essentially unchanged. However, with 3 or 5 wt.%, the martensitic α″ structure was found. When increased to 7.5 wt.% or greater, retention of the metastable β phase began. The ω phase was observed only in the Ti-10Zr-7.5Mo alloy. Among all Ti-10Zr-xMo alloys, the α″-phase Ti-10Zr-5Mo alloy had the lowest elastic modulus. It is noteworthy that all the Ti-10Zr and Ti-10Zr-xMo alloys had good ductility. In addition, the Ti-10Zr-5Mo and Ti-10Zr-12.5Mo alloys exhibited higher bending strength/modulus ratios at 20.1 and 20.4, respectively. Furthermore, the elastically recoverable angles of these two alloys (26.4° and 24.6°, respectively) were much greater than those of c.p. Ti (2.7°). Given the importance of these properties for implant materials, the low modulus, excellent elastic recovery capability and high strength/modulus ratio of α″ phase Ti-10Zr-5Mo and β phase Ti-10Zr-12.5Mo alloys appear to make them promising candidates.     

Ti-12Mo-6Zr-2Fe钛合金的纳米压入特征

利用纳米压入测量仪测试了Ti-12Mo-6Zr-2Fe钛合金的硬度和模量.测试表明,Ti-12Mo-6Zr-2Fe钛合金的硬度比Ti-6Al-4V ELI高,而模量比后者低,与常规方法得到的规律一致,表明该方法能很好地表征钛合金的力学特性.对测试过程的分析表明这种方法得到的结果不能与传统方法得到的结果互换,表面状态对测量结果有一定影响.     

Fatigue behaviour of boron free and boron containing heat treated Ti-13Zr-13Nb alloy for biomedical applications

Fatigue behaviour of heat treated Ti-13Zr-13Nb (TZN) and Ti-13Zr-13Nb-0.5B (TZNB) alloys for biomedical implants has been investigated by rotating bending test. It was found that fatigue strength of TZN and TZNB alloys is comparable with that of conventionally used biomedical titanium alloys. Addition of boron to TZN alloy deteriorates fatigue strength.     

Phase transformation behaviours and shape memory characteristics of Ti-45xNi-5Cu-xMo x=0.3-1.0 alloys

Abstract

Transformation behaviours and shape memory characteristics in Ti-45xNi-5Cu-xMo x=0.3, 0.5, or 1.0 at.- alloys were investigated by means of electrical resistivity measurements, differential scanning calorimetry, X-ray diffraction, thermal cycling tests under constant load, and tensile tests. The two stage transformation B2-B19-B19 occurred in Ti-45xNi-5Cu-xMo alloys, and complete separation of the B2-B19 transformation from the B19-B19 transformation was observed in Ti-44.0Mo-5Cu-1.0Mo at.- alloy. Substitution of Mo for Ni in Ti-45Ni-5Cu at.- alloy increased the critical stress for slip deformation and the pseudoelastic recovery. The maximum recoverable elongations of Ti-44.7Ni-5Cu-0.3Mo at.- and Ti-44.5Ni-5Cu-0.5Mo at.- alloys were 6.4 and 7 respectively.     

A study of the wetting,microstructure and bond strength in brazing SiC by Cu-X(X = Ti,V,Nb,Cr) alloys

In the active brazing of SiC by copper-based alloys, the effects of various active elements such as titanium, vanadium, niobium and chromium on the wetting, microstructure and bond strength are investigated. In wetting, Cu-Cr alloys have the lowest wetting angles on SiC of 10°–20° depending on the chromium content. SiC is decomposed on contact with alloy melts during brazing. Carbon and silicon released from this decomposition of SiC react with active elements to produce their carbides and suicides at the interface. The reacted layers have different microstructures depending on the brazing alloys, but Cu-Ti and Cu-Cr alloys show similar microstructure, as do Cu-V and Cu-Nb alloys. In the four-point bend tests, the brazed joints of Cu-5 at % Ti, Cu-5 at % V and Cu-5 at % Nb alloys have similar bend strengths of 86.9, 80.3 and 92.4 MPa, respectively. The brazed joints of Cu-2 at % Nb alloys show a high bend strength of 154 MPa, although the wetting angle is a little higher, at about 60°. Niobium is found as a new active element of copper-based alloys to braze SiC. Cu-Nb alloys are promising for substitution for Cu-Ti alloys.     

Anelastic relaxation due to hydrogen in Ti-35Nb-7Zr-5Ta alloy

Titanium and its alloys are frequently used in the production of prostheses and dental implants due to their properties, such as high corrosion resistance, low elasticity modulus, and high mechanical strength/density relation. Among the Ti-based alloys, Ti-35Nb-7Zr-5Ta (TNZT) is one that presents the smallest elasticity modulus (around 45 GPa), making it an excellent alternative to be used as a biomaterial. In this paper, mechanical spectroscopy measurements were made of TNZT alloys containing several quantities of hydrogen in solid solution. Mechanical spectroscopy measurements were made by using a torsion pendulum, operating at an oscillation frequency in the interval 2-20 Hz, temperature in the range 100-300 K, heating rate of about 1 K/min, and vacuum lower than 10⁻⁵ Torr. A relaxation structure and a reduction in the elasticity modulus were observed for the heat-treated and doped samples. The observed peak was associated with the interaction of hydrogen trapped by oxygen atoms around the titanium atom of the metallic matrix.     

Sintering behaviour of Ti-2Ni and Ti-5Ni elemental powders

The effect of nickel powder additions (2 and 5 at.%) on the sintering behaviour of titanium powder has been investigated through the dilatometric sintering study. The sintering of titanium powder was found to be enhanced significantly and the activation energies were decreased with increasing nickel content. The sintering of Ti-2 at.% Ni system at lower temperature was found to be controlled by Ti-Ti and Ti-Ni solid state sintering, whereas inter-diffusion dominates in Ti-5 at.% Ni sintering. At higher temperatures, sintering was found to be controlled by mixed mechanisms, i.e. inter-diffusion, chemical reaction and transient liquid phase formation.     

Comparison of microstructural evolution in Ti-Mo-Zr-Fe and Ti-15Mo biocompatible alloys

The microstructural evolution and attendant strengthening mechanisms in two biocompatible alloy systems, the binary Ti-15Mo and the quaternary Ti-13Mo-7Zr-3Fe (TMZF), have been compared and contrasted in this paper. In the homogenized condition, while the Ti-15Mo alloy exhibited a single phase microstructure consisting of large β grains, the TMZF alloy exhibited a microstructure consisting primarily of a β matrix with grain boundary α precipitates and a low volume fraction of intra-granular α precipitates. On ageing the homogenized alloys at 600 ^∘C for 4 h, both alloys exhibited the precipitation of refined scale secondary α precipitates homogeneously in the β matrix. However, while the hardness of the TMZF alloy marginally increased, that of the Ti-15Mo alloy decreased substantially as a result of the ageing treatment. In order to understand this difference in the mechanical properties after ageing, TEM studies have been carried out on both alloys in the homogenized and homogenized plus aged conditions. The results indicate that the ω precipitates dissolve on ageing in case of the Ti-15Mo alloy, consequently leading to a substantial decrease in the hardness. In contrast, the ω precipitates do not dissolve on ageing in the TMZF alloy and the precipitation of the fine scale secondary α leads to increased hardness.     

Microstructural Evolution of Infrared Brazed CP-Ti Using Ti-Cu-Ni Brazes

Microstructural evolution of infrared vacuum brazed CP-Ti using two Ti-based braze alloys,Ti-15Cu-15Ni and Ti-15Cu-25Ni,has been investigated.The infrared brazed joint consisted of eutectic Ti 2 Cu/Ti 2 Ni intermetallic compounds and Ti-rich matrix.The eutectic Ti 2 Cu/Ti 2 Ni intermetallic compounds disappeared from the joint after being annealed at 900 C for 1 h.In contrast,the depletion rate of both Cu and Ni from the braze alloy into CP-Ti substrate at 750 C annealing was greatly decreased as compared with that annealed at 900 C.Blocky Ti 2 Cu/Ti 2 Ni phases were observed even if the specimen was annealed at 750 C for 15 h.Because the Ni content of the Ti-15Cu-25Ni braze alloy is much higher than that of the Ti-15Cu-15Ni alloy,the amount of eutectic Ti 2 Cu/Ti 2 Ni phases in Ti-15Cu-25Ni brazed joint is more than that in Ti-15Ci-15Ni brazed joint.However,similar microstructural evolution can be obtained from the infrared brazed joint annealed at various temperatures and/or time for both filler metals.     

Study on Al-Cu-Si braze containing small amount of rare earth erbium

In the present work, the effect of a small amount of rare earth Er addition on the microstructure of Al-Cu-Si brazing alloy has been investigated. In the study, the Al-20Cu-7Si brazing alloys with various Er contents were prepared. 3003 aluminum alloy was chosen as a substrate. The microstructure of the brazed alloys was carefully observed. In addition, melting temperature, wettability and hardness of the brazing alloys were measured. The results indicate that the constituent of the microstructure of Al-20Cu-7Si-Er brazed alloy is similar to the Al-20Cu-7Si, which is mainly comprised of solid solutions of aluminum, silicon and the intermetallic compounds CuAl₂. When the Er content increases, the size of Al phases is decreased, and the filament-like or needle-like Si phase is thickened. The Si phases dominating in the shape of a filament or needle are transformed to those in the shape of a block when Er content is increased. Moreover, adding a small amount of Er can improve the wettability and hardness of the Al-20Cu-7Si brazing alloy. However, the melting temperature of the Al-20Cu-7Si alloy is almost unchanged when a small amount of Er is added.     

Microstructural Evolution of Ti-5.6Al-4.8Sn-2Zr-1Mo-0.35Si-0.7Nd Titanium Alloy with Carbon Additions

The effect of carbon addition on microstructural evolution was studied in a near-α titanium alloy(Ti-5.6Al-4.8Sn-2Zr-1Mo-0.35Si-0.7Nd). It was found that flake and ribbon titanium carbides with a NaCl crystal structure formed in the as-cast alloys with carbon additions of over 0.17 wt pct. Flake carbide particles are the product of eutectic transformation and precipitate from the high-temperature β phase. The ribbon carbide particles are primary phases formed prior to the nucleation of any metallic phases. The as-cast alloys with carbide precipitation after heat-treatment atβt-30℃ followed by water quenching showed the spheroidization of α lamellae and partial dissolution of carbide particles. After annealing at βt 15℃, carbide particles are mostly distributed at the grain boundary and spheroidized through mixed grain boundary plus bulk diffusions.     

Ti-6Al-3Nb-2Zr-1Mo合金室温压缩蠕变行为及位错类型研究

研究Ti-6Al-3Nb-2Zr-1Mo合金在不同外加应力下的室温压缩蠕变行为,拟合了蠕变曲线,计算出蠕变发生第二阶段的临界值,并对不同应力水平压缩后的合金显微组织进行TEM观察,研究其位错滑移类型.结果表明:室温条件下,Ti-6Al-3Nb-2Zr-1Mo合金压缩蠕变-时间曲线符合时间强化指数模型,该合金发生蠕变第二...     

The microstructural observation and wettability study of brazing Ti-6Al-4V and 304 stainless steel using three braze alloys

Both Ti-6Al-4V and 304 stainless steels (304SS) are good engineering alloys and widely used in industry due to their excellent mechanical properties as well as corrosion resistance. Well-developed joining process can not only promote the application of these alloys, but also can provide designers versatile choices of alloys. Brazing is one of the most popular methods in joining dissimilar alloys. In this study, three-selected silver base filler alloys, including Braze 580, BAg-8 and Ticusil®, are used in vacuum brazing of 304SS and Ti-6Al-4V. Based upon dynamic sessile drop test, Braze 580 has the lowest brazing temperature of 840°C, in contrast to 870°C for BAg-8 and 900°C for Ticusil® braze alloy. No phase separation is observed for all brazes on 304SS substrate. However, phase separation is observed for all specimens brazed above 860°C on Ti-6Al-4V substrate. The continuous reaction layer between Braze 580 and 304SS is mainly comprised of Ti, Fe and Cu. The thickness of reaction layer at Braze 580/Ti-6Al-4V interface is much larger than that at Braze 580/304SS interface. Meanwhile, a continuous Cu-Sn-Ti ternary intermetallic compound is found at the Braze 580/Ti-6Al-4V interface. Both Ticusil® and BAg-8 brazed joint have similar interfacial microstructures. Different from the Braze 580 specimen, there is a thick Cu-Ti-Fe reaction layer in both BAg-8/304SS and Ticusil®/304SS interfaces. The formation of Cu-Ti-Fe interfacial layer can prohibit wetting of BAg-8 and Ticusil® molten brazes on 304SS substrate. Meanwhile, continuous Ti₂Cu and TiCu layers are observed in Ti-6Al-4V/BAg-8 and Ti-6Al-4V/Ticusil® interfaces.     

Comparison of fatigue strengths of biocompatible Ti-15Zr-4Nb-4Ta alloy and other titanium materials

The fatigue strength of an annealed Ti-15Zr-4Nb-4Ta alloy at 1 × 10⁸ cycles was approximately 730 MPa. The fatigue strength of its alloy was much improved following an ageing treatment after a solution treatment. The tension-to-tension fatigue strengths of annealed Ti-6Al-4V, V-free Ti-6Al-7Nb, Ti-6Al-2Nb-1Ta, and Ti-15Mo-5Zr-3Al alloys at 1 × 10⁸ cycles were approximately 685, 600, 700, and 350 MPa, respectively. The ratios of fatigue strength at 1 × 10⁸ cycles to ultimate tensile strength for the α- and (α + β)-type Ti materials were higher than 65%.     

钎缝间隙对TC4与Ti3Al-Nb合金钎焊接头组织的影响

采用50Ti-20Zr-20Ni-10Cu粉末钎料对Ti3Al-Nb(Ti-13Al-24Nb)(质量分数)合金与TC4合金(Ti-6Al-4V)进行真空钎焊,通过SEM、EDS电子探针及拉伸试验,研究不同钎缝间隙的钎焊接头的显微组织及性能特征。结果表明,钎缝间隙对钎焊接头的组织及性能有较大影响,当钎缝间隙增大时,钎焊接头的组织变得复杂,在接头中既形成了共晶组织又形成了化合物带,这种组织特征会显著降低接头的强度。     

Study on Al-Cu-Si braze containing small amount of rare earth erbium

In the present work, the effect of a small amount of rare earth Er addition on the microstructure of Al-Cu-Si brazing alloy has been investigated. In the study, the Al-20Cu-7Si brazing alloys with various Er contents were prepared. 3003 aluminum alloy was chosen as a substrate. The microstructure of the brazed alloys was carefully observed. In addition, melting temperature, wettability and hardness of the brazing alloys were measured. The results indicate that the constituent of the microstructure of Al-20Cu-7Si-Er brazed alloy is similar to the Al-20Cu-7Si, which is mainly comprised of solid solutions of aluminum, silicon and the intermetallic compounds CuAl₂. When the Er content increases, the size of Al phases is decreased, and the filament-like or needle-like Si phase is thickened. The Si phases dominating in the shape of a filament or needle are transformed to those in the shape of a block when Er content is increased. Moreover, adding a small amount of Er can improve the wettability and hardness of the Al-20Cu-7Si brazing alloy. However, the melting temperature of the Al-20Cu-7Si alloy is almost unchanged when a small amount of Er is added.     

Effects of the relative contents of silver and copper on the interfacial reactions and bond strength in the active brazing of SiC

The roles of titanium in active brazing of SiC have been studied extensively, while studies on the roles of silver and copper, which constitute the major parts of the active brazing alloys, have been overlooked. The effects of the relative contents of silver and copper in the brazing alloy on the interfacial reactions and bond strength have been investigated in this study. The interfacial reactions can be divided into the decomposition reaction of SiC by the brazing alloy melt and the interfacial reaction of titanium with SiC. Brazing by the Cu-5at% Ti alloy induced SiC to be decomposed, but the addition of silver to the brazing alloy suppressed the decomposition of SiC. TiC and Ti₅Si₃ was produced from the interfacial reactions of titanium independent of the brazing alloys. However, their morphologies and formation mechanisms differ greatly depending on the relative contents of silver and copper. The bond strength and fracture modes are also dependent on the relative contents of silver and copper. A good bond strength of 159–178 MPa was obtained by brazing with the Ag-5at% Ti alloy at 985°C for 600 s and fracture initiates at the interface of the reaction product layer and propagates through SiC.     

Development of high Zr-containing Ti-based alloys with low Young's modulus for use in removable implants

This research focuses on the development of new titanium (Ti) alloys with a low Young's modulus for use in removable implants. In this study, Ti-30Zr alloy was selected as the base alloy, and the effect of Mo addition on the microstructures, Young's moduli, and tensile properties of Ti-30Zr-(0–8 wt.% Mo) alloys was investigated in this study to assess the mechanical compatibility of these alloys for biomedical applications. Further, the cytocompatibility of a part of the designed alloys was examined. The experimental results indicate that both the microstructures and the mechanical properties of the designed alloys are strongly affected by the Mo contents. The Ti-30Zr-(6, 7 wt.%) Mo alloys, located near the boundary of (β + ω)/β with a metastable structure, show a good combination of a low Young's modulus, high tensile strength, fairly large elongation. In addition, Ti–30Zr–7Mo alloy is highly cytocompatible.     

Formation of the carbonated hydroxyapatite film on Ti-30Zr-5Al-3V bio-alloy

The Ti-30Zr-5Al-3V titanium alloy has an ultra-low Young's modulus. So, it promises great application potential as a hard-tissue implanted biomaterial. However, its surface performances need to be improved before clinical applications. In this work, a carbonated hydroxyapatite film is deposited on the surface of Ti-30Zr-5Al-3V bio-alloy using electrochemical methods. Microstructure, film-substrate adhesion, and electrochemical corrosion behavior of carbonated hydroxyapatite deposited specimens in Ringer's solution are investigated. A homogeneous, dense, and fully covered carbonated hydroxyapatite film forms on the surface after depositing at 3 V, 90 °C for 120 minutes. The formation mechanism of the carbonated hydroxyapatite film on the micro-nano structure surface is revealed. The corrosion performance of carbonated hydroxyapatite deposited specimens in Ringer's solution is evaluated by using potentiodynamic polarization curves. The carbonated hydroxyapatite deposition obviously enhanced the corrosion resistance of the Ti-30Zr-5Al-3V bio-alloy.     

Oxidation behaviour of titanium-containing brazing filler metals

Brazements on alumina or partially stabilized zirconia (PSZ) of four silver- or copper-based brazing filler metals that contain titanium to promote wetting of and adherence to structural ceramics, were exposed in a thermogravimetric analyser at temperatures up to 700°C to atmospheres of 100% O₂, Ar-20% O₂ and Ar-3 p.p.m. O₂. The alloys included Cu-41.1Ag-3.6Sn-7.2Ti, Ag-44.4Cu-8.4Sn-0.9Ti, Ag-41.6Cu-9.7Sn-5.0Ti and Ag-37.4Cu-10.8In-1,4Ti, at%. All formed external oxides that were more or less protective under all of the test conditions studied. The growth of the oxides followed a parabolic time law. The gains in weight due to oxidation observed were small, ranging (for 45 h exposure at 400 °C to Ar-20% O₂) from 0.20 mgcm⁻² for the Ag-37.4Cu-10.8In-1.4Ti alloy to 0.46 mgcm⁻² for Cu-41.1Ag-3.6Sn-7.2Ti. As expected, weight gain increased with increasing temperature or . Unexpectedly, the titanium played a minor role in the scale formed on any of the filler metals with a titanium oxide, TiO₂, being found on only one alloy — Ag-41.6Cu-9.7Sn-5.0Ti. The brazements on PSZ gained weight at a higher rate than comparative brazements on alumina. We attribute this behaviour to oxygen transport through the zirconia resulting in the growth of an interfacial layer of titanium oxide.