Resistant Titanium Alloys Research Articles

Corrosion Resistant Titanium Alloys for Medical Tools and Implants

New corrosion resistant Ti-8Ni-Cr system alloys with increased hardness and strength have been developed for medical tools and implants. The development was made based on study of chromium influence on the phase constituents, microstructure, mechanical properties, corrosion resistance and electrochemical characteristics of Ti- 8Ni alloy. Optimum condition of thermal treatment, providing high strength, hardness and corrosion resistance of alloys has been defined – quenching from 950°C with content of chromium in alloys 1 – 3% (by addition of Yttrium in quantity 0,001 – 0,01 mass%). The cause is that alloys after quenching from 950°C have structure of transformed β-solid solution and contain ω-phase, which is micro dispersive during concentration of chromium up to 1-3%. On the base of studying of the phase equilibrium by microstructural, x-ray investigations and differential thermal analysis of Ti-8Ni-Cr system alloys polythermal sections of phase diagram of this system have been constructed, which is in complete accordance with the phase diagram formed by thermodynamic calculations. Study of mechanical properties of Ti-8Ni-(0-3) Cr quenching alloys show, that chromium increases the tensile strength (1000MPa) and hardness (48 HRC) and slightly influences on plastic properties of the Ti-8Ni alloy. Tensile strength of titanium commercial alloys: Ti-6Al-4V and Ti-5Al-3Sn do not exceed 900 MPA. Corrosion tests in medium containing human body: blood, physiological solution, gastric juice, tissue liquid and also corrosion testing according to the following regime: cleaning+disinfection+sterilization in aggressive solutions with addition of hydrogen peroxide reveal high corrosion resistance of Ti-8Ni-(0-3)Cr alloys, without the changing of surface. After 20 cycles corrosion losses of the commercial titanium alloys are ~ one order more than the losses of new alloys. Study of toxic properties of alloys Ti- 8Ni-(1-3)Cr during their implantation in muscles and abdominal cavity of animals show, that they do not cause local irritative actions on different tissues, they do not suppress local tissue reactions and do not have any toxic effects during short or long term implantation conditions. High corrosion resistance of alloy Ti-8Ni-1Cr is established also by the modeling and prediction of corrosion behavior in the physiological solution at the temperature 37oC with using of electrochemical investigations, spectral analysis, regression and variance analysis of the mathematical statistics. Alloys Ti-8Ni-(1-3)% Cr are recommended for manufacturing high-strength medical tools of multiply usage and surgical implants. Application of new alloys will allow improving functional properties and increase quality, reliability, service life of medical tools and implants.

Creep Damage Evaluation of Titanium Alloy Using Nonlinear Ultrasonic Lamb Waves

The creep damage in high temperature resistant titanium alloys Ti60 is measured using the nonlinear effect of an ultrasonic Lamb wave. The results show that the normalised acoustic nonlinearity of a Lamb wave exhibits a variation of the “increase-decrease" tendency as a function of the creep damage. The influence of microstructure evolution on the nonlinear Lamb wave propagation has been analyzed based on metallographic studies, which reveal that the normalised acoustic nonlinearity increases due to a rising of the precipitation volume fraction and the dislocation density in the early stage, and it decreases as a combined result of dislocation change and micro-void initiation in the material. The nonlinear Lamb wave exhibits the potential for the assessment of the remaining creep life in metals.

Thermal Flow Deformation Behavior and Mechanism of As-Cast and As-Extruded Burn Resistant Titanium Alloy

Hot compressive deformation tests of burn resistant titanium alloy (Ti-35V-15Cr-Si-C) with initially as-cast and as-extruded microstructure were performed at deformation temperature between 900°C to 1200°C for as-cast and 900°C to 1150°C for as-extruded alloy, and strain rates between 10-3s-1to 1s-1. The compressive true stress vs. true strain curves were measured, the deformation activation energy was calculated and the microstructures after deformation were studied. The results show that dynamic reversion is the primary soften mechanism of the burn resistant titanium alloy during hot deformation. At the higher strain rate ( =1s-1), the ‘Necklace’ Dynamic Recrystallization will occur for as-cast alloy, and a Continuous Recrystallization will occur for as-extruded alloy. At the lower strain rates, both as-cast and as-extruded burn resistant titanium alloy display the continuous recrystallization. The extruded alloy presents larger dynamic recrystallization regions than that of the as-cast alloy.

Ultrasound treatment of heat-resistant materials with compressed-air injection in the cutting zone

Tangential ultrasound vibrations of the cutting tool and compressed-air injection into the cutting zone are combined for the machining of heat resistant nickel and titanium alloys, which are of great importance in manufacturing today.

Fracture criterion for predicting surface cracking of Ti40 alloy in hot forming processes

Hot compression tests were conducted on Ti40 burn resistant titanium alloy in the temperature range of 900–1 100 °C and strain rate range of 0.01–10 s −1 to investigate its fracture behavior and critical fracture conditions in hot forming. It was observed that the failure of Ti40 alloy is attributed to longitudinal surface cracking due to severe oxidation of element V and the secondary tensile stresses. The critical fracture strain increases with increasing temperature and decreasing strain rate. From these observations and parallel FEM simulations, it was concluded that the critical fracture strain is a function of a single argument Zener-Hollomon parameter, and there is a linear relationship between them. An Oyane criterion successfully predicted the location of crack initiation. The critical fracture values also exhibit a liner relationship with ln Z. Based on these results, a new fracture criterion of Ti40 alloy based on Zener-Hollomon parameter was established.

Design, production and testing of a titanium exhaust duct for noise and weight reduction

AbstractHelicopter exhausts are usually basic components not yet developed to achieve the best noise reduction performance. This needs to change to continue complying with ever more restrictive noise regulations. A more efficient acoustic design could be reached using a complex configuration with assembly of multiple walls and 3D optimized geometry. As the exhausts nozzle are usually built out of Ni based alloys, the weight of such a component would increase. Such an increase could have a negative effect on the payload of the aircraft. Due to high temperatures and pressures of gas stream, Cp Titanium is limited for this application but heat resistant titanium alloys such as Beta21S and Ti 6–2‐4–2 would be a good substitution material as it provides significant weight reduction and capacity to sustain further power increase of the Helicopter engines. An European Project named “HORTIA” was funded to demonstrate the feasibility of using Heat and Oxidation Resistant Titanium Alloys for exhaust ducts in a noise and weight reduction objective. Studies were conducted on these materials to evaluate their mechanical performances and resistance against corrosion at high temperature for a service application. A thermo‐mechanical simulation of stress and temperature fields validated the definition design of a new component in an acoustically efficient configuration. An analysis of forming and welding parameters led to the industrial manufacturing of a complete exhaust with techniques like Super‐Plastic Forming and Laser Beam Welding. Finally the nozzle was successfully tested on en engine test bed for endurance and acoustic performance.

Creep feed grinding of gamma titanium aluminide and burn resistant titanium alloys using SiC abrasive

Following a brief introduction to titanium alloys and their machinability, the cutting performance of a gamma titanium aluminide intermetallic ( γ-TiAl) alloy: Ti–45Al–8Nb–0.2C wt% and a burn resistant titanium (BuRTi) alloy: Ti–25V–15Cr–2Al–0.2C wt%, is compared with creep feed grinding using SiC abrasive. The work utilised 2 separate L9 Taguchi fractional factorial arrays. Typically G-ratios were a factor of ∼10× greater for γ-TiAl than BuRTi, with on average ∼10% lower maximum power and ∼25% lower maximum specific energy for the γ-TiAl alloy. A combination of a moderately high wheel speed: 35 m/s, low depth of cut: 1.25 mm and low feed rate: 150 mm/min, produced the lowest average workpiece surface roughness (Ra∼1.4 μm). Workpiece surface integrity evaluation indicated that with lower operating parameter levels, in particular a wheel speed of 15 m/s, surfaces free of burn and cracks could be produced, while at higher wheel speeds: 35 m/s, extensive workpiece surface burn was evident, with the γ-TiAl alloy suffering extensive cracking. Microhardness measurements showed in some instances slightly increased workpiece surface hardness of around 50–60HK 0.025 for the BuRTi alloy and 200HK 0.025 for the γ-TiAl material over respective bulk hardness values of 375HK 0.025 and 400HK 0.025.

Current Research Situation and Development of Titanium Alloy in China in Recent Five Years

China pays great attentions to the development of titanium alloys and their basic theory because of their excellent properties. New titanium alloys and their new basic theories developed in China in recent five years were reviewed, for example, high temperature Ti alloys, burn resistant titanium alloys, high strength and middle strength titanium alloys and so on. The developing directions in the next 5 to 10 years were forecast.

Effect of Microstructures on Mechanical Properties of Heat Resistant Titanium Alloys at Elevated Temperatures

Effect of Microstructures on Mechanical Properties of Heat Resistant Titanium Alloys at Elevated Temperatures

The second phases in a burn resistant stable beta titanium alloy—Ti40

The second phases in Ti40 (Ti25V-15Cr-0.2Si) burn resistant titanium alloy are studied. The higher solution temperature, the more second phases in Ti40 alloy. There are not second phases if the solution temperature is below 850°C, while there are rod-like α and little Ti5Si3 phases if temperature is over 850°C. α, Ti5Si3 and oblique α′′ phases emerge after Ti40 solution at 910°C followed by aging at 600°C, while only Ti5Si3 phases emerge after solution at 860°C followed by aging at 600°C. The effect of the second phases on properties at RT are not obvious. There are different shapes of α and Ti5Si3 precipitates after Ti40 alloy exposure at 540°C for 100 h, which decreases the thermal stability.

耐熱チタン合金ＤＡＴ５４のミクロ組織および機械的性質に及ぼすＳｉ添加の影響

Daido Steel had developed a heat resistant titanium alloy DAT54 (Ti-5.8Al-4.0Sn-3.5Zr-2.8Mo-0.7Nb-0.35 Si- 0.06C), which is modified IMI834 and superior to it in serviceable temperature limit. It contains 0.35%Si as one of crucial alloying elements to precipitation-strengthen the alloy. In this study the effect of Si up to 0.95% was reinvestigated on its microstructure and mechanical properties.The silicon addition doesn't affect its liquidus, solidus nor beta-transus significantly, while it raises the solvus of titanium silicide, (Ti,Zr)5Si3, drastically over 1400K for 0.95%Si. The higher silicon increases the amount and the size of silicides retained at the solution treatment temperatures, beta-transus-35K. They tend to reduce the size of the pre-beta grains and the subsequent acicular colonies.The silicon improves tensile strength, creep-rupture life and fatigue limit, but the excessive silicon degrades tensile ductility and creep-rupture life. The Si content, 0.34%, is optimum to obtain the well-balanced properties. It is close to the solubility limit at the solution temperature and also to the nominal composition in DAT54.

Oxidation behavior of a burn resistant highly stabilized β titanium alloy

Ti40 alloy (Ti–25V–15Cr–0.2Si) is a highly stabilized β type burn resistant titanium alloy. Its oxidation behavior was studied. The weight gain increases greatly with the oxidation temperature, and then decreases when the oxidation temperature is over 1000°C. The oxidized products at 600°C are TiO 2 and V 2O 5. If the oxidation temperature is greater than 700°C, TiO 2 becomes the main product due to the vaporization of V 2O 5. The oxide scale cracks and peels off, if the temperature is over 900°C. SiO has been evidenced in the porous oxides if the temperature is over 800°C, and it vanishes as a result of scale spallation at 1050°C. A small amount of Cr 2O 3 has also been detected inside the scales and distributes non-continuously. Reasons of the fast oxidation are analyzed, and an oxidation model is suggested.

Simulating the cyclic mechanical response of titanium alloy 834 at 630°C

This paper explores features of observed material response under cyclic loading of a creep resistant titanium alloy, IMI 834. Methods of describing the material response are examined, particularly in the context of material models available in the ABAQUS finite element (FE) code. Isotropic, kinematic and combined hardening models are used to describe material behaviour under cyclic loading. Results from an earlier test programme are examined in detail, and the results are used to identify material constants. The models are implemented external to the FE code, and used to simulate the material response. Results from simulations are then compared with experimental results. It is found that the current ABAQUS models are not sufficiently detailed to provide an accurate representation of material behaviour, and additional parameters are required. The simulations overestimate the decrease the peak stress as a function of the number of cycles and underestimate the cyclic plastic strain range.

耐熱チタン合金ＤＡＴ５４製デュアルストラクチャーディスクの開発

耐熱チタン合金ＤＡＴ５４製デュアルストラクチャーディスクの開発

放電プラズマ焼結法による高耐食性チタン合金の試作

放電プラズマ焼結法による高耐食性チタン合金の試作

Ruthenium Enhanced Titanium Alloys

Several new, more highly corrosion resistant titanium alloys containing a nominal 0.1 weight per cent of ruthenium have been developed and evaluated for industrial service in corrosive environments. These improved ruthenium-enhanced α, α-β and β titanium alloys are lower in cost than the corresponding palladium-containing titanium alloys, and offer essentially the same corrosion performance in dilute reducing acids and hot brine environments. The titanium-0.1 ruthenium binary alloys can be cost effectively substituted for traditional titanium-palladium alloys and should represent a more attractive alternative to nickel-chromium-molybdenum alloys in hot, acidic brine applications. The corrosion database that has been established for the higher strength ruthenium-enhanced α-β and β titanium alloys in high temperature sweet and sour brines provides the basis for their selection for applications in the chemical process, oil/gas production, offshore and geothermal energy industries.

経済型耐隙間腐食性チタン合金（ＳＭＩ‐ＡＣＥ）の開発

経済型耐隙間腐食性チタン合金（ＳＭＩ‐ＡＣＥ）の開発

Structure and mechanical properties of the new VT25u heat-resistant titanium alloy

1. The VT25u alloy structure is typical of α+β alloys. A feature of this alloy when compared with the structure of other heat resistant titanium alloys is the wide variability of the constituents due to the high total alloying level in the alloy and the presence of tungsten which markedly reduces the diffusion rate. 2. The influence of the structure on the VT25u alloy mechanical properties is essentially similar to its effect on the properties of other heat-resistant α+β titanium alloys. At the same time, the VT25u alloy is characterized by a higher structural sensitivity of the plastic properties and the impact strength. Additionally, deviations are possible from the conventional effect of the structure type on the impact strength, if specimens with cracks (this is less for an alloy with a lamellar structure than for an alloy with a globular structure). The most probable cause of this anomaly is the silicide particles, which are mainly distributed at the grain boundaries in the lamellar structure, and which are larger and present in a greater quantity than is the case in the globular structure. 3. The optimum combination of properties for the VT25u alloy is achieved when 1120 N/mm2 ≤ σ2 0B ≤ 1200 N/mm2. Increasing σ2 0B may result in an inadmissable reduction in the ductility, impact strength, the ductile failure indices, and the multi and low cycle fatigue strength for notched specimens. 4. On a basis of the data obtained, as well as similar results obtained from other VT25u alloy semifinished products with varying structures and strength levels, a table has been produced for predicting the values of all the required properties.