Beta-type Titanium Alloy Research Articles

Improved fatigue properties with maintaining low Young's modulus achieved in biomedical beta-type titanium alloy by oxygen addition

Oxygen was added into biomedical β-type Ti-29Nb-13Ta-4.6Zr (mass%, TNTZ) alloy to improve its fatigue properties with maintaining its low Young's modulus. The effect of oxygen on the fatigue behaviors of these oxygen-added TNTZ alloys was systematically investigated. A series of TNTZ-(0.1, 0.3, 0.5 and 0.7 mass%)O alloys were prepared, denoted as 0.1O, 0.3O, 0.5O, and 0.7O, respectively. The Young's moduli of the prepared alloys increase slightly with increasing oxygen content; 0.7O possessing the highest oxygen content still shows a quite low Young's modulus. The fatigue limits of the alloys increase monotonically with oxygen content increases. The high-concentration oxygen in 0.7O suppresses the slip plane decohesion and induces the formation of densely-arranged small-scaled α" martensite twins that increases the paths and distance for fatigue crack propagation, thus it enhances the resistance to the fatigue crack initiation and propagation in 0.7O, which contributes to its excellent fatigue performance. Among all the alloys compared in the present study, 0.7O shows a high fatigue limit of ~ 635MPa, a high tensile strength of ~ 1100MPa, a large elongation of ~ 20% as well as a low Young's modulus of ~ 76GPa, thus it is regarded as a promising biomaterial for next-generation biomedical applications.

Improved Corrosion Resistance of Metastable Beta Ti-X (X = 6Mn, 8Cr, and 36Nb) Binary Alloys As a Function of 10.Wt% Mo Equivalence

Beta type titanium alloys are developed as metallic biomaterials due to their low elastic modulus compared to well-known Ti-6Al-4V alloy. Since Mo is known to be an efficient beta phase stabilizer, Ti-Mo binary alloy have been extensively studied on their microstructural characteristics, mechanical properties and corrosion resistance. The stability of the beta phase can be expressed using the “molybdenum equivalent” which has minimum critical value of 10-11 .wt%. Niobium is well known to be very good to resist against corrosion in simulated body fluid and presents an excellent biocompatibility. Mn was selected as an alloying element due to its beta stabilizing effect, low cytotoxicity, high availability and lower cost when compared to other popular alloying elements. Cr-induced passive layer has been proven to be strong and solid. Ti-Cr based alloys also have been widely used for dental applications. In this study, the amount of alloying additions were calculated as a function of 10 .wt% Mo equivalence in order to evaluate the corrosion performance of each alloy. Potentiodynamic polarization test and time-based electrochemical impedance spectroscopy (EIS) were used to evaluate the corrosion behavior in Ringer’s solution. It was found that the corrosion parameters obtained from potentiodynamic polarization test were not significantly different to those of Ti-10Mo alloy. Substituting Mo to the other studied elements simply shifts the corrosion potential into less-noble zone. However, the overall corrosion current density were lower compared to those of Ti-10Mo alloy. The lowest corrosion current density observed in Ti-6Mn alloy with the value of 7.742 nA/cm2, which 8 times lower than those of Ti-10Mo with the value of 48.81 nA/cm2. Impedance responses increase with increasing immersion time. There is little difference in the profiles in the high- and medium-frequency regions, but at lower frequencies the difference becomes substantial. The solution-film resistance element remains low for different immersion times at lower potentials, while film-substrate resistance increases with time. At higher potentials, both resistance have comparable values, pointing to the increased protectiveness, or less defective structure, of the outer porous layer at higher potentials. This result agrees with XPS evaluation on the passive film which formed on their most stable formation within the working potential range. At OCP, the capacitance values increase with the time. While at higher potentials, the capacitance values remain constant with time.

Biocompatible mechanical surface modification processing and mechanical properties of beta-type titanium alloys

Biocompatible mechanical surface modification processing and mechanical properties of beta-type titanium alloys

Extending the application of plasma electrolytic oxide coatings to novel low-rigidity beta-type titanium alloys: applications to load-bearing orthopaedic implants

Extending the application of plasma electrolytic oxide coatings to novel low-rigidity beta-type titanium alloys: applications to load-bearing orthopaedic implants

The Role of Stress Induced Martensite in Ductile Metastable Beta Ti-alloys Showing Combined TRIP/TWIP Effects

A new family of metastable beta type titanium alloys has recently been designed for ductility improvement with large strain-hardening effect. Superior plastic properties were obtained due to collective effects of both phase transformation induced plasticity and twinning induced plasticity. A series of stress induced phase transformations, including stress/strain-induced beta to omega transformation and stress-induced martensitic beta to α” transformations, play particular roles at each deformation stage. The SIM transformations were found to be closely related to the strain-hardening behavior of the material. In this work, the relationship between SIM transformations and strain-hardening effect were studied by microstructural investigations.

Mechanical Performance and Biocompatibility of Biomedical Beta-Type Titanium Alloy Subjected to Micro-Shot Peening

Beta-type Ti-29Nb-13Ta-4.6Zr (TNTZ) was recently developed as a representative biomedical Ti alloy. As-solutionized TNTZ has a low Young’s modulus less than 60 GPa close to that of cortical bone along with very low cytotoxicity and good bone biocompatibility. Solution treatment and aging (STA) is a typical heat treatment for improving the mechanical properties of beta-type titanium alloys. However, STA also drastically increases the Young’s modulus. Therefore, this study investigated the effects of surface modification, micro-shot peening, on the mechanical properties of TNTZ subjected to severe thermomechanical treatment in order to maintain a relatively low Young’s modulus. The bone contact characteristics of TNTZ samples subjected to surface modification and cancellous bone were also compared. The Vickers hardness of cold-swaged TNTZ (TNTZSW) subjected to micro-shot peening was significantly increased within 20 mm from the very edge of the specimen surface. The fatigue strength of TNTZSW subjected to micro-shot peening increased especially in the high cycle fatigue life region. The fatigue limit was around 400 MPa. The bone formations on TNTZSW subjected to micro-shot peening and TNTZSW with the mirror surface as comparison material were almost identical to each other. However, the relative bone contact ratio of TNTZSW subjected to micro-shot peening was better than that of TNTZSW with the mirror surface.

Biomedical Polymer Surface Modification of Beta-Type Titanium Alloy for Implants through Anodic Oxide Nanostructures

Anodic oxide nanostructures (nanopores and nanotubes) were formed on a biomedical β-type titanium alloy, Ti–29Nb–13Ta–4.6Zr alloy (TNTZ), in order to improve adhesive strength by the anchor effect of a segmented polyurethane (SPU) with soft tissue compatibility. The nanotube structure was formed beneath the nanoporous structure. The adhesive strength between the SPU coating and the nanoporous structure formed on TNTZ by anodization is more than 1.5 times that of an SPU coating on as-polished TNTZ with a mirror finish. After removal of the nanoporous structure by etching with HF solution, the adhesive strength of the SPU coating on the exposed nanotube structure is decreased.

Biofunctional Surface Layer and its Bonding Strength in Low Modulus β-Type Titanium Alloy for Biomedical Applications

Recently, low-modulus β-type titanium alloys have been the focus of considerable attention because of their high biocompatibility and their low moduli that make them effective for inhibiting bone atrophy and for enhancing bone remodeling. However, the biofunctinalities of titanium alloys, such as bone conductivity, blood compatibility, and soft tissue compatibility, are poor. Therefore, surface modification techniques such as bioactive ceramic surface modification and blood-and soft-tissue-compatible polymer surface modification are applied to titanium alloys. Hydroxyapatite (HAp) surface modification via metal organic chemical vapor deposition (MOCVD) and segmented polyurethane (SPU) surface modification via silane coupling treatment are effective techniques to add biofunctionalites to titanium alloys. HAp surface modification via MOCVD and SPU surface modification using three kinds of silane coupling agents on a low modulus beta-type titanium alloy, namely, TNTZ, are discussed. Moreover, the bonding strengths of HAp and SPU on the surface of TNTZ, which are important parameters, are also discussed.

Effects of micro- and nano-scale wave-like structures on fatigue strength of a beta-type titanium alloy developed as a biomaterial

Some newly developed β-type titanium alloys for biomedical applications exhibit distinctive heterogeneous structures. The formation mechanisms for these structures have not been completely revealed; however, understanding these mechanisms could lead to improving their properties. In this study, the heterogeneous structures of a Ti–29Nb–13Ta–4.6Zr alloy (TNTZ), which is a candidate for next-generation metallic biomaterials, were analyzed. Furthermore, the effects of such heterogeneous structures on the mechanical strength of this alloy, including fatigue strength, were revealed by comparing its strength to that of homogenous TNTZ. The heterogeneous structures were characterized micro-, submicro- and nano-scale wave-like structures. The formation mechanisms of these wave-like structures are found to be different from each other even though their morphologies are similar. It is revealed that the micro-, submicro- and nano-scale wave-like structures are caused by elemental segregation, crystal distortion related to kink band and phase separation into β and β′, respectively. However, these structures have no significant effect on both tensile properties and fatigue strength comparison with homogeneous structure in this study.

밀도함수 이론법으로 설계한 고강도 Ti 합금 특성 분석

Titanium and its alloys offer the highest strength, excellent corrosion resistance and the highest strength to weight, but their disadvantage is a higher cost. This study was made to obtain useful information on their high-strength properteis for designing beta type titanium alloys using the DV-Xα method. To lower prices low-cost elements (Mo, Al, Fe) were used. The Mechanical properties of these alloys are compared to commercial alloys in order to investigate the characteristics of the alloys. The results showed strength of the titanium alloys was somewhat higher (30-90 MPa) than conventional alloys. †(Received September 28, 2012)

Phase Constitution and Heat Treatment Behavior of Low Cost Ti-Mn System Alloys

This paper is a review of results for Ti-Mn [1], Ti-Mn-Al [2] and Ti-Mn-Fe [3] alloys that have been previously published. Titanium alloys, especially beta-type titanium alloys, have high specific strength, excellent corrosion resistance and good biocompatibility. Unfortunately, applications of titanium alloys are limited by their relatively higher cost. One reason is the use of rare and expensive metallic elements, such as vanadium and molybdenum, as a beta stabilizer. In order to reduce the cost, inexpensive and abundantly available metallic elements should be used as beta stabilizers. Manganese was adopted as a beta stabilizer because it is an abundant metallic element in the Earth’s crust and is relatively low in cost. The heat treatment behavior of Ti-Mn, Ti-Mn-Al and Ti-Mn-Fe alloys was investigated through electrical resistivity and Vickers hardness measurements, X-ray diffraction measurements to identify phase constitution, and observations using a light microscope [1], [2] and [3].

Research and Development of Low-Cost Titanium Alloys for Biomedical Applications

β-type titanium alloys comprising low cost elements such as Fe, Mn, Cr, Sn, Al, O and N and having low Young’s modulus are currently being developed. Examples of such alloys include Ti-10Cr-Al, Ti-Mn, Ti-Mn-Fe, Ti-Mn-Al, Ti-Cr-Al, Ti-Sn-Cr, Ti-Cr-Sn-Zr, Ti-(Cr, Mn)-Sn, and Ti-12Cr. Ti-5Fe-3Nb-3Zr belongs to that class of titanium alloys in which rare metals such as Nb, Ta, and Zr have been reduced using Fe. Ti-5Fe-3Nb-3Zr has a Young’s modulus of around 76 GPa and has greater strength than that of Ti-6Al-4V ELI for biomedical applications. The characteristics of Ti-5Fe-3Nb-3Zr and other low-cost beta-type titanium alloys with low Young’s moduli are discussed from the viewpoint of biomedical applications.

High Performance Beta Titanium Alloys as a New Material Perspective for Cardiovascular Applications

During the last few decades, titanium alloys are more and more popular and developed as biomedical devices because of their excellent biocompatibility, very good combination of mechanical properties and prominent corrosion resistance [1-3]. Recently, a new generation of beta titanium alloys dedicated to biomedical applications has been developed. Based on biocompatible alloying elements such as Ta, Nb, Zr and Mo, these alloys were designed as low modulus alloys [4] or nickel-free superelastic materials [5, 6] mainly for orthopedic or dental applications as osseointegrated implants. Beta type titanium alloys take great advantages from their capacity to display several deformation mechanisms as a function of beta phase stability. Therefore, from low to high beta stability, stress assisted martensitic phase transformation (β-α’’), mechanical twinning or simple dislocation slip can alternatively be observed [7]. As a consequence, a very large range of mechanical properties can be reached, including low apparent modulus, large reversible elastic deformation or high yield stress. Although titanium alloys display now a long history of successful applications in orthopedic and dental devices, none of them have been commercially exploited in the area of coronary stents, despite their superior long term haemocopatibility compared to the 316L stainless steel. However, according to previous researches on the biocompatibility of various metals, the corrosion behavior of stainless steel is dominated by its nickel and chromium components, which may induce redox reaction, hydrolysis and complex metal ion–organic molecule binding reactions, whereas none are observed with titanium [8, 9].

レーザ加熱による表面溶体化処理を応用した β 型チタン合金の表面時効硬化処理とその摩耗特性

レーザ加熱による表面溶体化処理を応用した β 型チタン合金の表面時効硬化処理とその摩耗特性

Superplasticity of Ti2448 Alloy with Nanostructured Grains

Ti-24Nb-4Zr-8Sn, abbreviated as Ti2448 from its chemical composition in weight percent, is a multifunctional beta type titanium alloy with body centered cubic (bcc) crystal structure, and its highly localized plastic deformation behavior contributes significantly to grain refinement during conventional cold processing. In the paper, the nanostructured (NS) alloy with grain size less than 50 nm produced by cold rolling has been used to investigate its superplastic deformation behavior by uniaxial tensile tests at initial strain rates of 1.5x10(-2), 1.5x10(-3) and 1.6x10(-4) s(-1) and temperatures of 600, 650 and 700 degrees C. The results show that, in comparison with the coarse-grained alloy with size of 50 mu m, the NS alloy has better superplasticity with elongation up to,similar to 275% and ultimate strength of 50-100 MPa. Strain rate sensitivity (m) of the NS alloy is 0.21, 0.30 and 0.29 for 600, 650 and 700 degrees C, respectively. These results demonstrate that grain refinement is a valid way to enhance the superplasticity of Ti2448 alloy.

Surface Age Hardening and Wear Properties of Beta-Type Titanium Alloy by Laser Surface Solution Treatment

Surface Age Hardening and Wear Properties of Beta-Type Titanium Alloy by Laser Surface Solution Treatment

Screw Form Rolling of Beta Type Titanium Alloy Preliminary Worked by Torsion

Beta type titanium alloys in a cold processability are light, have high strength, excellent corrosion resistance and the same level as Young's modulus of human bone. Therefore, beta type titanium alloys are used for plant facilities such as nuclear plants, architectural materials, aircraft, car, biomaterial, medical equipment, glasses and golf club head, etc. Microstructure and mechanical properties of beta type titanium alloys processed by rolling and heat treatment have been reported [1]. Additionally, screw form rolling using beta type titanium alloys has also been reported [2]. However, the development in those characteristics after the preliminary working by torsion has been unknown.

Mechanical anisotropy and ideal strength in a multifunctional Ti–Nb–Ta–Zr–O alloy (Gum Metal)

Abstract An ideal shear strength of Gum Metal, a newly developed set of beta-type titanium alloys with the nominal composition Ti-24(Nb + V + Ta) – (Zr, Hf) – O (at.%) believed to deform without motion of crystal dislocations, has been investigated experimentally for precise determination. Tensile tests of single crystals of Gum Metal along the <100>, <110>, and <111> directions showed that the Young' moduli were 40, 60, and 86 GPa, respectively. The elastic constants were estimated as c11 – c12 = 25 – 27 GPa and c44 = 29 – 36 GPa. In terms of these values, the anisotropy factor and the ideal strength were evaluated as 2.3 – 2.6 and 1.7 – 1.9 GPa, respectively. It was found that a ratio of the actual ultimate tensile strength to the ideal strength for Gum Metal was much higher than for other bcc metals.

Dental Precision Casting of Ti-29Nb-13Ta-4.6Zr Using Calcia Mold

The objective of this study is to develop a dental precision casting process for a beta-type titanium alloy, Ti-29Nb-13Ta-4.6Zr (TNTZ) alloy which has been developed for biomedical applications, using a mold made by electrically fused calcia particles. The effect of a combination of different sizes of calcia particles on the surface condition of the mold was investigated. In addition, to obtain a smooth surface, a cast TNTZ was made using a mold made using a mixture of calcia particles with a wax pattern conducted with calcia slurry coatings. Furthermore, surface reaction layer of the cast TNTZ was evaluated using an optical microscopy, a Vickers' hardness test and a X-ray diffractometry. The surface of the mold fabricated with a mixture of fine (diameter < 0.3 mm) and coarse (diameter = 1-3 mm) calcia particles is smooth and showed no cracks or defects. In addition, the surfaces of the cast TNTZ made using the duplex-coated wax pattern with the fine pure calcia slurry and crushed silica fiber-reinforced fine calcia slurry are very fine. Furthermore, the formation of the surface reaction layer on the cast TNTZ is remarkably inhibited. The results of this study should lead to enhancements in the creation of cast TNTZ for dental products.

Characteristics of Biomedical Beta-Type Titanium Alloy Subjected to Coating

Beta-type titanium alloys used in biomedical applications have been developed all over the world. In particular, Ti-29Nb-13Ta-4.6Zr alloy (TNTZ) is one of beta-type titanium alloys for biomedical applications that has been developed by the authors in Japan. Although TNTZ is composed of non-toxic elements such as niobium, tantalum, and zirconium, it still lacks bioactivity, which is the ability to form chemical bonds with living bones. The stems that are parts of artificial hip joints, dental implants, etc., which are made of metallic materials, etc. are required to bond strongly with living bones. However, these stems, dental implants etc., cannot form chemical bond with living bones by themselves. The bioactive surface modification of metallic materials by the application of ceramics is effective in improving the biocompatibility of TNTZ. Calcium phosphate ceramics such as hydroxyapatite (Ca 10 (PO 4 ) 6 OH 2 ; HAP) and β-tricalcium phosphate (β-Ca 3 (PΟ 4 ) 2 ; β-TCP) possess bioactivity. In this study, the characteristics and morphology of TNTZ coated with a calcium phosphate invert-glass-ceramic (CPIG) layer by dip-coating treatment or with a sodium titanate layer by alkali solution treatment are investigated before and after soaking it in a simulated body fluid (SBF). The bonding strength between a CPIG layer with a thickness of around 5 μm and a specimen surface of TNTZ is around 25 MPa. No cracks or exfoliations are observed along the boundary between the CPIG layer and the specimen surface. This is the reason why the difference in the thermal expansion coefficients between CPIG layer and TNTZ reduced due to a compositional gradient zone with a thickness of around 3 μm in CPIG layer. HAP is formed on the entire surface of the TNTZ specimen after soaking it in the SBF for more than 1728 ks. The fatigue properties of TNTZ coated with a CPIG layer are similar to those of as-solutionized TNTZ. A reticulate structure with a thickness of 400 to 800 nm is formed on the TNTZ specimen surface after soaking it in 3 to 10 kmol/m 3 NaOH solution for 86.4 ks and 172.8 ks. HAP is completely formed on the entire surface of the TNTZ specimen when it is soaked in the SBF for 1209.6 ks after being soaked in 5 kmol/m 3 NaOH solution for 172.8ks.