Heat-treated Titanium Alloy Research Articles

High-Temperature Tribology of Selective Laser-Melted Titanium Alloys: Role of Adhesive Wear

Abstract Titanium alloys (Ti6Al4V) are emerging materials used in many engineering applications, especially aerospace, due to their strength-to-weight ratio, corrosion resistance, and high specific strength. The selective laser melting (SLM) process is vividly used to fabricate components with minimum material usage, which reduces the total weight of the product. The hard particles in the atmosphere repeatedly hit the aircraft turbine blades in a rotary motion during aircraft operations. Due to significant sliding action between articulating surfaces, these turbine blades need good wear resistance. With this motivation, rotary wear tests were performed under high vacuum at three different temperatures: room temperature, 400 °C, and 850 °C on as-built and heat-treated titanium alloy fabricated by the SLM process. The parameters like the speed, number of cycles, time, and high vacuum were considered to be constant while performing these high-temperature tribology experiments. As-built and heat-treated samples against the alumina ball resulted in lower coefficient of friction (COF) values at high temperatures compared to room temperature. In addition, adhesive wear was found to be the dominant wear mechanism at high temperatures. From the morphological studies, plowing strips, plowing ridges, and shallow grooves were significantly noticed on the worn-out surfaces of the heat-treated samples. Although low COF values were obtained at high temperatures on tested samples, higher specific wear-rates were seen in these samples due to the continuous removal of soft material.

Дослідження тривалої жаростійкості титанових матеріалів для гібридних паливних комірок

Hybrid SOFC-MGT systems, which combine a solid oxide fuel cell (SOFC) and a gas microturbine (MGT) are capable of generating clean energy with high efficiency. Compared to large turbines in aviation and other areas of mechanical engineering and energetics, the requirements for mechanical properties of MGT materials in SOFC may be less strong, but one of the most important is resistance to long-term oxidation. For SOFC materials it is considered that oxidation resistance test duration must be not less than 1000 h. In addition, today there is a tendency to developing average-temperature (550—650 oC) SOFC modifications. Physical and mechanical properties, the long-term (1000 hours) oxidation resistance at 600 °C in particular, for a number of titanium alloys and composites depending on their chemical and phase composition and production method have been studied. These materials are promising for gas microturbines of a hybrid system “solid oxide fuel cell — gas turbine”. Cast, thermally deformed (forging, rolling), and heat-treated titanium alloys and also sintered and hot-pressed titanium composites have been investigated. They were compared to the most widely used in mechanical engineering and other industries Ti—6Al—4V alloy. It was shown that materials of the Ti—Al—X system (X = C, Nb, Mo) based on titanium MAX phases with nanolaminate microstructure have an advantage. At the same time, alloys based on titanium aluminides γ-TiAl / α2-Ti3Al in the cast state have the highest long-term heat resistance, as well as the best complex of physical and mechanical characteristics among the studied materials. Keywords: titanium alloys, chemical and phase composition, mechanical properties, long - term heat resistance, fuel cell.

Revealing the WEDM Process Parameters for the Machining of Pure and Heat-Treated Titanium (Ti-6Al-4V) Alloy.

Ti-6Al-4V is an alloy that has a high strength-to-weight ratio. It is known as an alpha-beta titanium alloy with excellent corrosion resistance. This alloy has a wide range of applications, e.g., in the aerospace and biomedical industries. Examples of alpha stabilizers are aluminum, oxygen, nitrogen, and carbon, which are added to titanium. Examples of beta stabilizers are titanium–iron, titanium–chromium, and titanium–manganese. Despite the exceptional properties, the processing of this titanium alloy is challenging when using conventional methods as it is quite a hard and tough material. Nonconventional methods are required to create intricate and complex geometries, which are difficult with the traditional methods. The present study focused on machining Ti-6Al-4V using wire electrical discharge machining (WEDM) and conducting numerous experiments to establish the machining parameters. The optimal setting of the machining parameters was predicted using a multiresponse optimization technique. Experiments were planned using the response surface methodology (RSM) technique and analysis of variance (ANOVA) was used to determine the significance and contribution of the input parameters to changes in the output characteristics (cutting speed and surface roughness). The cutting speed obtained during the processing of the annealed titanium alloy using WEDM was quite large as compared to the cutting speed obtained in the case of processing the pure, quenched, and hardened titanium alloys using WEDM. The maximum cutting speed obtained while processing the annealed titanium alloy was 1.75 mm/min.

A Review on Additive Manufacturing of Titanium Alloys for Aerospace Applications: Directed Energy Deposition and Beyond Ti-6Al-4V

Titanium alloys are expensive and difficult to process into large complex components for aerospace applications. Directed energy deposition (DED), one of the additive manufacturing (AM) technologies, offers a high deposition rate, being suitable for fabricating large metallic components. So far, most review articles on the AM of titanium discuss the popular powder bed fusion method with the emphasis on the “workhorse” titanium alloy—Ti-6Al-4V. There have been few review articles on the DED process of a broad range of titanium alloys—near-α, β, and other α + β alloys beyond Ti-6Al-4V. This article focuses on the processing–microstructure–property relationships in the DED-processed titanium alloys (Ti-6Al-4V and beyond) with the following aspects: (1) microstructure evolution induced by solidification, thermal cycles, and post-processing heat treatment; (2) tensile properties of as-deposited and heat-treated titanium alloys; (3) defects, residual stresses, and fatigue properties; and (4) micro/nanomechanical properties. The article concludes with perspectives about future directions in this field.

Orthogonal machining of Heat Treated Ti-10-2-3: FE and Experimental

ABSTRACT Nowadays, finite element analysis is the best suitable approach to reduce the need for several experiments. This paper is based on the FE modeling and model validation via the experimental value of turning operation in 2D on heat-treated Titanium alloy (Ti-10-2-3 is also named as Ti-10 V-2Fe-3Al). Turning operation is treated as an orthogonal cutting process and this operation is simulated using Abaqus® explicit 6.14 software, with the help of Johnson–Cook material constructive model with boundary conditions. FE simulation results were validated with experimentally obtained forces and cutting temperatures during turning operation on different cutting thickness. Simulation and the experiment were conducted on the three different heat-treated conditions of the Ti-10-2-3 like Solution Treatment and Aging (STA), Annealed and Solution Treated and Overaged (STOA). The model validation showed that the average errors in the prediction and the experimental values are cutting force 4%, feed force 3% and temperature 11%. In this model, the simulated value of the average feed force was slightly less than the experimental value due to the consideration of actual friction between tool–chip interfaces on the rake face.

The Microstructural Difference and Its Influence on the Ballistic Impact Behavior of a Near β-Type Ti5.1Al2.5Cr0.5Fe4.5Mo1.1Sn1.8Zr2.9Zn Titanium Alloy.

In this work, a near β-type Ti5.1Al2.5Cr0.5Fe4.5Mo1.1Sn1.8Zr2.9Zn alloy was hot-rolled at the temperature of 800–880 °C with a thickness reduction of 87.5% and then heat-treated with the strategy of 880 °C/1 h/air cooling (AC) + 650 °C/3 h/AC. The microstructure difference between the hot-rolled and heat-treated titanium alloys and its influence on the ballistic impact behavior of the hot-rolled and heat-treated titanium alloys were analyzed. The microstructural investigation revealed that the average size of the acicular secondary α phase (αs) dropped from 75 to 42 nm, and the corresponding amount of this phase increased significantly after heat treatment. In addition, the dislocation density of the α and β phases decreased from 0.3340 × 1015/m2 and 4.6746 × 1015/m2 for the hot-rolled titanium alloy plate to 0.2806 × 1015/m2 and 1.8050 × 1015/m2 for the heat-treated one, respectively. The high strength of the heat-treated titanium alloy was maintained, owing to the positive contribution of the acicular secondary α phase. Furthermore, the critical fracture strain increased sharply from 19.9% for the hot-rolled titanium alloy plate to 23.1% for the heat-treated one, thereby overcoming (to some extent) the constraint of the strength–ductility trade-off. This is mainly attributed to the fact that the dislocation density and the difference between the dislocation densities of the α and β phases decreased substantially, and deformation localization was effectively suppressed after heat treatment. Damage to the hot-rolled and heat-treated titanium alloy plates after the penetration of a 7.62 mm ordinary steel core projectile at a distance of 100 m was assessed via industrial computer tomography and microstructure observation. The results revealed that a large crack (volume: 2.55 mm3) occurred on the rear face and propagated toward the interior of the hot-rolled titanium alloy plate. The crack tip was connected to a long adiabatic shear band with a depth of 3 mm along the thickness direction. However, good integrity of the heat-treated titanium alloy plate was maintained, owing to its excellent deformation capability. Ultimately, the failure mechanism of the hot-rolled and heat-treated titanium alloy plates was revealed by determining the crack-forming reasons in these materials.

Tensile Properties of Vacuum Heat-treated Ti6Al4V Alloy Processed by Selective Laser Melting

This study presents an investigation on the tensile behaviour of heat-treated titanium alloy (Ti6Al4V) parts, which have been manufactured by Selective Laser Melting (SLM) additive manufacturing. The parts were heat treated at a temperature of 850°C for 2 hours with and without Argon inert gas in a vacuum furnace. The tensile properties of the SLM samples with and without heat treatment have been compared to evaluate the mechanical performance of the 3D printed samples. The ultimate tensile strength (UTS) of as built Ti6Al4V part was found to be 1175 MPa. The UTS of heat-treated Ti6Al4V sample in vacuum without Argon gas was found to be 750MPa, while the UTS of heat-treated sample in vacuum with Argon gas was recorded as 980MPa. These values compare well with other published values of UTS for SLM built Ti6Al4V alloys with similar heat-treated conditions. The work also studied the micro-hardness of all the samples and compared the values with each other and found that the heat treated sample have lower average Vickers hardness values compared to as built samples.

Influence of tool inclination angle and cutting direction on long thin-walled part’s dimensional and geometric accuracy when high-speed ball end milling the heat-treated titanium alloy Ti–6Al–4 V

Thin-walled parts are often used in various industrial applications and due to their functional requirements, higher accuracies are generally desired. But due to their low stiffness characteristics, deformation and chatter problems are frequently encountered in their machining, thus resulting in poor accuracy. Moreover, due to 5-axes milling, which is usually required for finish machining of such parts, further complexities in the process are added and, consequently, achieving higher accuracy becomes more challenging. Therefore, in this study, the influence of tool inclination angle and feeding direction has been investigated on the resultant surface accuracy of thin cantilever shaped parts in finish milling conditions through experiments, finite element method simulations and theoretical discussions. Moreover, since work material’s microstructure and hardness also have key influence on its machinability, therefore, the effect of heat treatment state on resulting surface accuracy also has been explored. Three different titanium alloy, Ti–6Al–4 V specimens have been used. Two of the specimens were given solution treatment at 1050 ℃/1 h followed by aging at 550 ℃/4 h. One of the specimens after being solution treated was allowed to cool in air while the other was cooled in water to obtain different microstructure and hardness whereas the third specimen was used in as-received condition (casted). The three Ti–6Al–4 V specimens were machined at five different tool inclination angles (60°, 70°, 75°, 80°, and 85°) with two feeding directions (horizontal inwards and vertical inwards). Results have shown that the angle near the perpendicular to the surface i.e. 85° (5° away from the perpendicular) has lowest deformation value and also has better surface quality, which shows that the lowest effective cutting speed at this angle has helped in achieving higher accuracy. Moreover, among the cutting directions studied, vertical inward direction produces smoother surface due to its less pushing effect on the surface being cut as compared to horizontal inwards direction. And in terms of heat treatment state, the specimen which was cooled in air after being solution treated has produced better results for all cutting conditions studied, mainly attributed to fine homogenous lamellar α + β Ti–6Al–4 V structure achieved due to slow cooling rate of air. Analysis of variance using response surface methodology has been carried out to develop predictive model and to study the influence of each variable on the accuracy. The developed model has shown good accuracy when validated through additional experiments.

Influence of microstructure and hardness on machinability of heat-treated titanium alloy Ti-6Al-4V in end milling with polycrystalline diamond tools

The main objective of this paper is to develop the relationship between microstructure and machinability of titanium alloy Ti-6Al-4V which is given heat treatment beyond β transus temperature, with the help of milling experiments using polycrystalline diamond (PCD) tools. Two of the specimens were solution treated at 1050 °C/1 h. After the treatment, one of the specimen was cooled in water while the other specimen was air-cooled, followed by aging treatment at 550 °C/4 h. The third specimen was used in as-received condition (casted). Cutting speed, feed rate, and depth of cut were varied, and their effects have been analyzed on cutting forces, vibration amplitude, temperature, and tool wear for all the three specimens. The results have shown improved and better machinability for the specimen which was cooled in air after the solution treatment with PCD tools. This behavior of the alloy is mainly attributed to formation of homogeneous lamellar α + β Ti-6Al-4V microstructure. Although, the air-cooled specimen has higher hardness than the as-received specimen. But, the former alloy’s fine homogeneous and lamellar α + β Ti-6Al-4V microstructure as compared to the microstructure of the latter specimen (irregular α + β Ti-6Al-4V structure) and absence of α’ secondary precipitate (found in water-cooled specimen) has helped in giving improved performance. Thus, from this study, it can be concluded that machinability of titanium alloy Ti-6Al-4V can be further improved with controlled heat treatment process using PCD tools.

Mitigation of the Wear Failure of Ti-6Al-4V Dental Biomedical Implant by Isothermal Treatment

Ti-6Al-4V alloy has been in use as dental implants till date because of its favorable mechanical properties. However, it wears off over a period of time in the oral cavity. Bearing this problem in mind, this research aims at mitigating the wear failure of Ti-6Al-4V dental implant via isothermal treatment. The as-received Ti-6Al-4V was cut and machined into 30 mm × 25 mm × 3 mm for abrasive wear samples. The samples were solution heat-treated at 960 °C accompanied by the aging process at 480 °C for varying soaking times of 2, 4, 6, and 8 h. The samples for wear analysis were subjected to abrasive wear using a three-body abrasive wear test machine with varying loads of 5 and 15 N, and silica sand was used as the abrasive medium. From the result, the wear rate of the heat-treated titanium alloy increased with the applied load, and the samples aged for 8 h showed 99 and 98% wear resistance at 5 and 15 N, respectively. In the present study, it was established that isothermal aging can be employed to enhance the wear resistance of Ti-6Al-4V alloy for use in biomedical applications.

Investigation on the Microstructures and Tensile Properties of TA15 Titanium Alloy Thick-Wall Parts Formed by Laser Rapid Forming Process

TA15 titanium alloy thick-wall parts have been deposited by Laser rapid forming (LRF) process. In this paper, a new overlap method between two adjacent laser tracks has been used to deposit the thick-wall titanium part. Results showed that the LRFed thick-wall titanium part was good in shape by using the new overlap method. The microstructure of the LRFed titanium alloy primarily consists of columnar prior-beta grain, which is perpendicular to the substrate resulting from directionally solidification. It also could be observed that the size of alpha phase increased with increasing laser power and decreasing scanning velocity. Tensile properties of LRFed titanium was slightly lower than that of the wrought annealed TA15 titanium alloy, after the heat-treatment of 940°C/1h/AC, the heat-treated titanium alloy showed good tensile properties which were equivalent to that of the wrought annealed TA15 titanium alloy.

Microscopy of heat treated titanium alloy BT16

Metallographic characterisation is combined with statistical analysis to study the microstructure of a BT16 titanium alloy after different heat treatment processes. It was found that the length, width and aspect ratio of α plates in this alloy follow the three-parameter Weibull distribution. Increasing annealing temperature or time causes the probability distribution of the length and the width of α plates to tend toward a normal distribution. The phase transformation temperature of the BT16 titanium alloy was found to be 875±5°C.

Creating laminar composites from titanium alloys

The development of composite laminar materials based on heat-treated VT23 and VT15-1 titanium alloys is considered. For composites consisting of VT23 or VT15-1 alloy (the hard component) and OT4 alloy (the soft component), increasing the number of layers and reducing their thickness enhances the plasticity. Composites with the soft component at the surface are stronger.

生体活性チタン合金のin vivo骨界面強度(J10-2 チタン系材料の展開と応用技術,J10 チタン系材料の力学・強度特性と応用技術)

Pure titanium and titanium alloy are generally used as orthopaedic implants like total hip arthroplasty because of its high strength and high biocompatibility. Stability of bone-implant interfacial bonding is a critical factor for successful total hip arthroplasty. Because of the problems of loosening and dissolution of harmful ion with cemented techniques, alternative cement-less fixation of the total hip arthroplasty has been developed. Plasma spray coating of bone-like apatite is an example to add strong bonding capability with bone to metallic materials. However, this physical coating treatment shows weak base-coating bonding strength and difficult to apply on irregular surface. Chemical treatments do not have such drawbacks. The alkali-heat treatment method, developed by Kokubo et al, is a kind of chemical treatment to enhance the bone-bonding strength of pure titanium. This technique involves soaking the implant in an alkali solution and subsequent heating, resulting in a strong bone-bonding ability and a high bone affinity. This study transplants alkali heat treated titanium alloy on the rabbit femoral bone and examined in vivo interfacial bonding strength.

Enhancement of bone‐bonding strengths of titanium alloy implants by alkali and heat treatments

The purpose of this study is to evaluate the bone-bonding ability of alkali- and heat-treated titanium alloys. Smoothed-surface rectangular plates of Ti6Al4V, Ti6Al2Nb1Ta, and Ti15Mo5Zr3Al were prepared. The plates were inserted transcortically into the proximal metaphyses of bilateral rabbit tibiae, with alkali- and heat-treated plates inserted on the right side, and untreated plates on the left. The tensile failure loads between the implants and the bones were measured after 8, 16, and 24 weeks by a detaching test. The untreated implants showed almost no bonding even at 16 weeks, and only weak bonding at 24 weeks. In contrast, treated implants showed bonding to bone at all time periods. Histological examination showed that alkali- and heat-treated alloys bonded directly to the bone. Conversely, the untreated implants had an intervening layer of fibrous tissue between the bone and the plate, or only partial direct contact with the bone. This study demonstrates that alkali and heat treatments enhance the bone-bonding strength of these titanium alloys. Although in this study even tentative conditions of the treatments enhance the bonding strength of the titanium alloys, further work is required to determine the optimum conditions for treatment to give the highest bonding strength. These new bioactive titanium alloys are available for weight-bearing and bone-bonding orthopedic devices. © 1999 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 48: 689–696, 1999

Enhancement of bone-bonding strengths of titanium alloy implants by alkali and heat treatments.

The purpose of this study is to evaluate the bone-bonding ability of alkali- and heat-treated titanium alloys. Smoothed-surface rectangular plates of Ti6Al4V, Ti6Al2Nb1Ta, and Ti15Mo5Zr3Al were prepared. The plates were inserted transcortically into the proximal metaphyses of bilateral rabbit tibiae, with alkali- and heat-treated plates inserted on the right side, and untreated plates on the left. The tensile failure loads between the implants and the bones were measured after 8, 16, and 24 weeks by a detaching test. The untreated implants showed almost no bonding even at 16 weeks, and only weak bonding at 24 weeks. In contrast, treated implants showed bonding to bone at all time periods. Histological examination showed that alkali- and heat-treated alloys bonded directly to the bone. Conversely, the untreated implants had an intervening layer of fibrous tissue between the bone and the plate, or only partial direct contact with the bone. This study demonstrates that alkali and heat treatments enhance the bone-bonding strength of these titanium alloys. Although in this study even tentative conditions of the treatments enhance the bonding strength of the titanium alloys, further work is required to determine the optimum conditions for treatment to give the highest bonding strength. These new bioactive titanium alloys are available for weight-bearing and bone-bonding orthopedic devices.

Diamond coating of titanium alloys at tempering temperature

Polycrystalline diamond films have been deposited on pure titanium and Ti-6Al-4V in a microwave plasma reactor from CH 4-H 2 and CO-H 2 gas mixtures, at a temperature in the range 600–900 °C. X-ray diffraction, scanning electron microscopy and Raman spectroscopy showed that 1–10 μm diamond layers could be produced at 600 °C with a fairly good crystallinity and residual stresses limited to about 5 GPa. The intrinsic properties of the heat-treated titanium alloys are maintained at this tempering temperature and no spalling occurred when an appropriate pretreatment was carried out. Therefore we expect that diamond-coated titanium alloys could be used for general engineering applications where a low friction coefficient, low wear rate and load-bearing capacity are all necessary.

Microstructure and Tensile Ductility in a β Heat Treated Titanium Alloy

The nature of tensile failure in aβ-treated titanium alloy, Ti-6Al-l.6Zr-3.3Mo-0.3Si, is demonstrated to be strongly dependent on cooling rate followingβ treatment. A characterization of microstructure, the fracture surface of tensile tested samples, and the associated slip behavior shows the fracture mode to be determined by the microstructure as well as composition of the a laths. A martensitic matrix with fine grain boundary α particles leads to intergranular failure. At slower cooling rates, α laths form as side plates from grain boundary allotriomorphs, and an fcc interface phase is present at thea lath/retainedβ interfaces. This microstructure results in transgranular fracture caused by ductile failure at the α lath/β interfaces within the grains rather than at grain boundary ⇌. If the composition is equilibrated across the a laths by a long-term anneal followingβ treatment, the slip mode becomes extremely planar leading to slip band related cracking across the grains.

Strength of heat treated titanium alloy cans

1. We showed that the strength of cans made of extruded pipes of heat treated titanium alloys can reach 124–147 kg/mm2. 2. The use of high-temperature thermomechanical treatment increases the strength of cans made of the VT16 alloy and considerably improves the structure.

Deformation of a duplex titanium alloy

The deformation of a titanium alloy containing 6% aluminium and 4% vanadium has been studied. It is shown that on the average the grains of the primary alpha phase were subjected to less deformation than the specimen. From these observations it is concluded that the phenomenon of “beta embrittlement” in heat-treated titanium alloys is not due to increased deformation of the beta phase as a result of the elimination of the relatively soft alpha grains.