Alpha-beta Alloys Research Articles

Resolving high-strain-rate scratch behavior of Ti6Al4V in experiment and meshless simulation

The outstanding strength-to-weight ratio and corrosion resistance of titanium have made it the material of choice in the aerospace industry and medicine. The alpha–beta alloy Ti6Al4V is particularly preferred for its excellent mechanical and bio-compatible properties. Despite its advantages, the low thermal conductivity and poor tribological performance of titanium pose significant challenges during manufacturing and in operation. This research offers deep insights into the high strain rate behavior of Ti6Al4V under abrasive load, such as e.g. experienced in machining, by modifying the standard scratch test setup and using optimized Johnson–Cook material parameters to perform Material Point Method (MPM) simulations. The MPM simulations provide accurate predictions of the data gathered through high strain rate scratch experiments. We found an increase in the von Mises stress distribution as well as the normal and tangential forces required to perform a scratch of the same depth as the strain rate increases. The morphology of the scratch profiles also showed an increase in the height of the ridges that form as the scratching speed increases. These findings are in line with the increase in yield strength and work hardening with growing strain rate. This study bridges the gap between simulation models and experimental observations by providing insights for improved machining strategies and surface treatments that can enhance the performance of Ti6Al4V in demanding applications.

Plasma spheroidisation and characterisation of commercial titanium grade 5 powder for use in metal additive manufacturing

Low density, high strength, high corrosion resistance, and biocompatibility are some of the attractive characteristics of parts produced through additive manufacturing from Ti6Al4V powder. This alpha-beta alloy is the workhorse of the titanium industry, and it is applied for manufacturing of structural components of aircraft, hydraulic systems, engine components, helicopter rotor blades, rockets and spacecraft. In the study presented in this paper, a plasma spheroidisation process was used to develop spherical powder from irregularly shaped commercial titanium Grade 5 powder. Properties of the powder relevant to metal additive manufacturing, namely particle shape and size, chemical composition, flow characteristics and density, were determined to establish the usability of the developed powder. It was concluded that plasma spheroidisation of irregularly shaped Ti6Al4V Grade 5 powder for AM application was feasible for powder size ranges between 45 and 150 μm, because the oxygen content did not increase for size fractions in this range.

Optimal Cutting Conditions of Abrasive Waterjet Cutting for Ti-6Al-2Sn-2Mo Alpha-Beta Alloy Using EDAS and DFA Methods

Abrasive waterjet machining (AWJM), a known metal cutting process in manufacturing, is likely to be improved with the selection and use of the most influential parameters in machining decision-making. This work illustrates the development of two multicriteria indicators to optimize parameters for the abrasive waterjet machining process, providing optimization information for the surface morphology problem. The evaluation based on the distance from average solution (EDAS) method was used as the first indicator while the desirability function analysis (DFA) method reflects the second indicator. The results demonstrate a huge promise of both indicators, EDAS and DFA, to develop procedures for optimizing the parameters of Ti-6Al-2Sn-4Zr-2Mo alpha-beta alloy through the abrasive waterjet machining process. For the EDAS method, experimental trial 7 provided the best results with the water jet pressure of 220 bar, traverse speed of 40mm/min, and standoff distance of 1mm. The corresponding material removal rate is 151.667mm3/min while the roughness average is 2.76mm. The DFA method also provided the same results as those of the EDAS method. The present study is evidence of optimization of the parameters of Ti-6Al-2Sn-4Zr-2Mo alpha-beta alloy using the AWJM process. This warrants an intervention to enhance productivity and the economic gains of the company.

Experimental Investigation and Optimization of Process Parameters in Ti – (6242) Alpha–Beta Alloy Using Electrical Discharge Machining

This investigation exposes electrical discharge machine (EDM) technique in expelling the metal with a conducted copper electrode from the Ti–6Al–2Sn–4Zr–2Mo alloy. The alloy Ti–6Al–2Sn–4Zr–2Mo has the highest resistance, high-temperature detection, high tensile strength, and high yield strength. Ti–6Al–2Sn–4Zr–2Mo alloy is commonly used for applications such as aerospace, medical equipment, automotive parts, and nuclear power plants. EDM provides easy machinability and excellent surface finishes. Machine parameters of primary noteworthiness, such as Discharge Current (I), Spark on time (μs), and Tool Diameter (mm), are considered using the Taguchi L27 orthogonal array. Metal removal rate (MRR), tool wear rate (TWR), and overcut (OC) perpendicularity are investigated with the help of mean effective plots. Multi response optimization to maximize the material removal rate (MRR) and minimize the tool wear rate (TWR) and over cut (OC) on the surface of the workpiece has been analyzed by Grey relational analysis (GRA). The result expresses that spark on time (Ton) contributes (6.22%) more on affecting the machining characteristics followed by electrode diameter (76.97%) and discharge current (16.97%). From the F-test, it is assumed that all the machining parameters have a significant influence on responses. Accordingly an optimum combination of machining parameters is also determined.

ATI 3-2.5

Abstract ATI 3-2.5 is a Titanium-3Aluminum-2.5Vanadium alloy that has higher strength than unalloyed titanium and is much more amenable to cold working than Ti-6Al-4V. This near-alpha, alpha-beta alloy is generally used in the annealed or cold-worked and stress-relieved conditions. This datasheet provides information on composition, physical properties, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: Ti-166. Producer or source: ATI.

Advancements of Superplastic Forming and Diffusion Bonding of Titanium Alloys for Heat Critical Aerospace Applications

<div class="section abstract"><div class="htmlview paragraph">Titanium’s high strength-to-weight ratio and corrosion resistance makes it ideal for many aerospace applications, especially in heat critical zones. Superplastic Forming (SPF) can be used to form titanium into near-net, complex shapes without springback. The process uses a machined die where inert gas is applied uniformly to the metal sheet, forming the part into the die cavity. Standard titanium alpha-beta alloys, such as 6Al-4V, form at temperatures between 900 and 925°C (1650-1700°F). Recent efforts have demonstrated alloys that form at lower temperatures ranging between 760 and 790°C (1400-1450°F). Lowering the forming temperature reduces the amount of alpha case that forms on the part, which must be removed. This provides an opportunity of starting with a lower gauge material. Lower forming temperatures also limit the amount of oxidation and wear on the tool and increase the life of certain press components, such as heaters and platens. A variation of this process is SPF combined with Diffusion Bonding (SPF/DB) of two or more titanium sheets to produce integrally stiffened structures with limited fasteners and less weight than comparable components. The four sheet process utilizes two core sheets with a welded cell pattern and two face sheets that are welded together along the periphery. Inert gas pressure is then applied at elevated temperature to form the sandwich structure. Recent studies have shown that dissimilar alloys with different grain sizes and flow stresses can be sufficiently diffusion bonded together. Using lower temperature alloys as the core sheet material allows the entire structure to be formed and bonded at a lower temperature regardless of the flow stress of the face sheets.</div></div>

Development of High Temperature Oxidation Resistant Titanium Alloy Arconic-THORTM

The aeroengine and airframe applications of titanium alloys are often limited by their insufficient oxidation resistance to the aggressive environment at higher temperatures. A high temperature oxidation resistant titanium alloy (Arconic-THORTM) has been developed. This alloy is an alpha-beta alloy with superior oxidation resistance and improved creep resistance. The oxidation weight gain of Arconic-THORTM is much lower than Ti-6242 and Beta 21s in the temperature range up to 750˚C. The room and elevated temperature properties of Arconic-THORTM are comparable to those for Ti-6242. Arconic-THORTM also shows superior, post-thermal-exposure tensile strength, ductility, and fatigue properties, and is capable of being cold formed, hot formed, and superplastic formed, welded and heat treated to different product geometries. The microstructures and mechanical properties for sheet manufactured from the production ingots are presented and discussed in this study.

Material Ductile Failure-Based Finite Element Simulations of Chip Serration in Orthogonal Cutting of Titanium Alloy Ti-6Al-4V

Titanium alloy Ti-6Al-4V, an alpha-beta alloy, possesses ductile deformation behavior and offers advantageous properties, light weight but high strength, good resilience, and resistance to corrosion, becoming highly suitable for aerospace and biomedical applications. However, its machinability is still considered a limiting factor in improving productivity. This paper presents a finite element modeling methodology for orthogonal cutting titanium alloy Ti-6Al-4V by considering material constitutive modeling together with material ductile failure in combination with damage initiation and cumulative damage-based evolution to simulate not only ductile material separation from workpiece to form chips but also chip serration mechanism by applying an elastic–viscoplastic formulation. The finite element model is further verified with orthogonal cutting experiments (using both uncoated and TiAlN-coated carbide tools) by comparing simulated and acquired forces and simulated and captured chip images at high cutting speeds. The effects of cutting speed, feed, tool rake angle, and tool coating on the degree of chip serration are studied through the simulation results. The cutting temperature and strain distributions are obtained to study the chip serration mechanism under different cutting conditions. It is confirmed that the material failure, crack initiation, and damage evolution are of great significance in the chip serration in cutting titanium alloy Ti-6Al-4V.

Friction Stir Processing Trials of SP-700 (Ti-4.5Al-3V-2Fe-2Mo) Titanium Alloy

Superplastic titanium alloy (SP-700 with nominal composition of Ti-4.5Al-3V-2Fe-2Mo) an alpha-beta alloy, with a beta-rich fine microstructure and excellent superplastic formability has wide applications in aerospace components, metal wood heads, tools, automotive components. However, very little information is available regarding friction stir processing (FSP) characteristics of this alloy. This study discusses the trials of FSP of this highly formable titanium alloy. Results are discussed in terms of hardness and temperature measurements and microstructural observations.

Microstructure and Mechanical Properties of Ti-Al-Mo-V-Ta Alloys

P/M Ti-Al-Mo-V-Ta alpha-beta alloys were processed by hot-pressing sintering technique. The effects of Ta additions on microstructure and properties of the Ti-5Al-4Mo-4V alloys were investigated using X-ray diffraction, optical microscope, scanning electron microscope and mechanical properties tests. The results show that minor Ta addition improves the relative density and the mechanical properties of P/M Ti-5Al-4Mo-4V alloys. After sintering for 4h at 1623 K, the relative density and compression strength of Ti-5Al-4Mo-4V-5Ta alloy are 99.3% and 1950 MPa.

Effect of Process Parameters in Electric Discharge Machining of Ti-6Al–4V Alloy by Three Different Tool Electrode Materials

The effect of process parameters namely peak current, pulse on time and flushing pressure on electrical discharge machining (EDM) of titanium alloy (Ti–6Al–4V) were investigated by using three different tool electrode materials namely copper, brass, and aluminium. Kerosene is used as dielectric. The process parameters for machining Ti6Al4V are varied at three levels by using Taguchi's orthogonal array table. The responses such as Metal Removal Rate (MRR), Tool Wear Rate (TWR), and Surface Roughness (SR) are measured and the most significant parameter was confirmed by ANOVA (Analysis Of Variance). The test result shows that copper electrode material possesses higher MRR, less TWR as compared to brass and aluminium. Brass and copper tools has good surface finish as compared with aluminium. The finest electrode material for machining of Ti6Al4V alpha beta alloy in EDM process was in the order of copper, brass and aluminium.

Milling of gamma titanium–aluminum alloys

The present research is focused on the machinability of the gamma-TiAl alloys, also called in literature as titanium aluminides, under the milling process. In comparison with the alpha–beta alloys, the alloys solidified in the gamma phase present improved ratio between strength and density even at higher temperatures; however, hard and new machining problems appear. Currently, there is a lack of machining parameters for this kind of materials, and therefore, its inclusion in aeronautical and automotive applications is being delayed. This work summarizes the results of a testing program which offers an outlook on the cutting conditions when machining even more difficult-to-cut titanium alloys than the more spread and known structural alpha–beta alloys.

Mechanical properties and microstructure of an α + β titanium alloy with high strength and fracture toughness

The Ti-Al-Sn-Zr-Cr-Mo-V-Si (Ti-62A) alloy, an alpha-beta alloy with high strength and fracture toughness, is currently used as an advanced structural material in aerospace and non-aerospace applications. Thermo-mechanical processes can be used to optimize the relationship between its strength and fracture toughness. A Ti-62A alloy bar can be machined through a transus β-forged plus α+β solution treated and aged specimen with a lamellar alpha microstructure. The effects of heat treatment on the mechanical properties were discussed. Heat treatment provided a practical balance of strength, fracture toughness, and fatigue crack growth resistance. A comparison of the Ti-62A alloy with the Ti-62222S alloy under the same thermo-mechanical processing conditions showed that their properties are at the same level.

Microstructural evolution during sintering of the blended elemental Ti–5Al–2.5Fe alloy

The Ti–5Al–2.5Fe (in wt.%) alpha-beta alloy was processed by powder metallurgy using the blended elemental (BE) technique. Samples of this alloy were prepared by cold pressing followed by vacuum sintering between 973 and 1673 K. The holding time at each temperature was 2 h. The sintering behavior of both elemental (Ti + Al + Fe) and intermetallic (Ti + Fe 2Al 5 + TiAl 3) powder mixtures and their corresponding microstructural evolution were investigated. Scanning electron microscopy (SEM) in the backscattered mode was used to image the samples. The chemical composition of the individual phases was determined by standardless energy-dispersive spectrometry (EDS) in SEM. Sintered densities were determined by conventional gravimetric method. The aim of the present work is to compare the sintering behavior and the nature of the evolving phases during sintering of BE–Ti–5Al–2.5Fe alloy using both elemental and intermetallic powders.

Low-cost titanium alloys? Iron may hold the answers

Spanish researchers have been looking at means of using alloying elements such as iron and chromium to make low-cost titanium alloys. They are not commonly used in conventional titanium processing, but PM techniques can avoid such problems as segregation and provide a way to develop new beta or alpha-beta alloys. They describe work on blending titanium powder with different iron-based powders to obtain alpha-beta alloys…

TIMETAL 6-2-4-6

Abstract Timetal 6-2-4-6 is an alpha-beta alloy with greater strength in thicker sections than Timetal 6-4. This datasheet provides information on composition, physical properties, elasticity, and tensile properties as well as creep and fatigue. It also includes information on forming. Filing Code: TI-141. Producer or source: Timet.

TIMETAL 551

Abstract Timetal 551 is an improved-strength version of Timetal 550 alloy that retains good forging characteristics. The alpha-beta alloy has a nominal composition of Ti-4Al-4Mo-4Sn-0.5 Si, and it is used in gas turbine engine parts. This datasheet provides information on composition, physical properties, elasticity, tensile properties, and shear strength as well as creep. It also includes information on high temperature performance as well as forming and heat treating. Filing Code: TI-138. Producer or source: Timet.

Influence of Oxygen Content on the Mechanical Properties of Titanium-35Niobium-7Zirconium-5Tantalum Beta Titanium Alloy

Abstract Titanium-35Niobium-7Zirconium-5Tantalum beta titanium alloy (also known as TiOsteum® beta titanium alloy) is a new metallic biomaterial that was designed to have outstanding osseointegratabilty, good mechanical strength, improved ductility, very low elastic modulus, and good hot and cold workability [1]. In this study, mechanical property data are presented from several TiOsteum alloy production lots with ingot oxygen contents ranging from 0.05 to 0.68 %. Additionally, mill annealed mechanical property data collected over the last 10 to 15 years for the more common alpha, alpha-beta, and beta titanium alloys are presented as a function of oxygen content and compared to TiOsteum alloy. The influence of oxygen as an interstitial strengthening element is well established in titanium alloys. This study examines this effect over a broad range of oxygen values, and has significance for the application of the new TiOsteum alloy and other beta titanium alloys being considered for use in medical and surgical devices.

Comparisons of surface roughnesses and sliding resistances of 6 titanium-based or TMA-type archwires

Six titanium-based or TMA-type archwires (Beta III, Resolve, CNA, TMA, low-friction ion-implanted TMA or TMAL, and TiMolium) were studied as functions of composition, morphology, surface roughness, and sliding mechanics by using a scanning electron microscope, an x-ray energy dispersive wavelength analyser, a laser specular reflectometer, and a frictional testing machine. In the last instrument, all wires were coupled with 0.022-in stainless steel brackets in which normal forces were applied by 0.010-in stainless steel ligatures. With regard to composition, 5 wires were true beta-titanium alloys having nominal compositions of 80% titanium, 10% molybdenum, 6% zirconium, and 4% tin, and 1 was an alpha-beta alloy having a nominal composition of 90% titanium, 6% aluminum, 3% vanadium, and 1% other. Morphologies varied from surfaces with striations, scale, or layers of drawn material that suggested surface steps or fissures. Specular reflectance and optical roughness measurements divided the archwires into 2 groups of 3: Beta III, Resolve, and CNA had an overall mean value of 0.148 microm; and TMA, TMAL, and TiMolium had a mean overall value of 0.195 microm. These roughness measurements and their accompanying details of the compositional analyses suggested that there could be as few as 2 vendors manufacturing the 5 beta-titanium products. For 6 different values of angulation that embraced the passive and active regions of sliding, the coefficients of friction varied rather narrowly from 0.17 to 0.27 and were independent of surface roughnesses. Although these contemporary products are better than their predecessors of over a decade ago, other issues might be more important than surface finishes or frictional resistances because all products appear fairly comparable.

A New Alpha-Beta Alloy, Ti-4.5Al-4Cr-0.5Fe-0.2C, Solution Hardened by Ultra High Content of Carbon

A New Alpha-Beta Alloy, Ti-4.5Al-4Cr-0.5Fe-0.2C, Solution Hardened by Ultra High Content of Carbon