Low-cost Titanium Alloy Research Articles

A comparative study of microstructure and texture evolution in low cost titanium alloy swarf and powder recycled via FAST and HIP

A comparative study of microstructure and texture evolution in low cost titanium alloy swarf and powder recycled via FAST and HIP

Analysis of abnormal bright band characteristics of forging for a new low-cost titanium alloy

A centimeter-scale defective microstructure, namely abnormal bright band characteristics (ABBC), is found in engineering production of titanium alloy forgings, and it seriously affects the stability and reliability of performance. The targeted work for the reason of the formation of the ABBC is carried out in this paper. The ABBC contains a large number of small colony α, without grain boundary. The α phase in the ABBC includes 12 variants from one β grain. The crystallographic orientation of reconstructed β phase in the ABBC is a standard cube texture. The formation of the ABBC is caused by the abnormal grain growth (AGG) of cube-grain. The cube-grain is a low energy storage grain, which can merge with other grains to grow rapidly.

Dry Sliding Wear Behavior of Experimental Low-Cost Titanium Alloys

The high cost and potential toxicity associated with the common commercial Ti-6Al-4V alloy are major concerns against its continued use in the biomedical industry. Low-cost, less toxic titanium alloys have been developed as a possible alternative to Ti-6Al-4V. Because of the various wear processes that take place in the human body, it is imperative to have a good understanding of the wear properties and wear resistance of these alloys. This study, therefore, investigated the resistance to wear of the low-cost Ti-3Fe, Ti-4.5Al-1V-3Fe, and Ti-4.5Al-1V-3Fe alloys under dry sliding conditions in contrast to the common commercial alloy, Ti-6Al-4V. The findings revealed that among the tested alloys, Ti-3Fe exhibited the lowest resistance to wear as it displayed the highest coefficient of friction (0.55) and wear rate (5.55E-06 mm3/Nm). The Ti-4.5Al-1V-3Fe alloy demonstrated superior wear resistance compared to the rest of the alloys, including Ti-6Al-4V, as it had the lowest wear rate (4.27E-06 mm3/Nm) and wear volume (0.0026 mm3). Overall, the experimental alloys displayed very similar wear resistance to Ti-6Al-4V, making them promising commercial alloys that can replace Ti-6Al-4V in bioimplant applications.

Joint effect of Mo and Cr on microstructure and properties of Ti–Al–Mo–Cr–B alloys

Innovative Ti–3Al-xMo-yCr-0.1B (x = 4, 2, 4; y = 2, 4, 4, wt.%) alloys were developed via powder metallurgy by varying the contents of Mo and Cr. The aim is to reduce costs and attain outstanding performance by introducing relatively affordable alloying materials. The results display that all alloys feature lamellar microstructure, including α, β and TiCr2 phases. The appropriate combination of alloying elements can greatly increase the relative density value of the alloy to 99.34% (e. g. Ti–3Al–4Mo–4Cr-0.1B). The strength of these alloys is greatly improved (>1028 MPa) due to solid solution strengthening and αs/β interface strengthening. Ti–3Al–4Mo–2Cr-0.1B alloy shows the optimum properties combination with the tensile strength and ductility of 1080 MPa and 5.4%. The wear test results show that the wear resistance of the three alloys is much better than that of pure titanium. Ti–3Al–4Mo–4Cr-0.1B has the best wear resistance which could be the outcome of solid solution strengthening and higher density. Meanwhile, Ti–3Al–4Mo–4Cr-0.1B possesses the highest corrosion resistance with the Ecorr and Icorr of −0.15 V and 0.039 μA/cm2, which is attributed to the presence of more β phase and highest density. This work offers a good idea for creating low-cost titanium alloys with great strength and high density and provides the possibility to apply titanium alloys extensively.

Ti-5Fe spherical powder alloy prepared by electrode induction gas atomization processes (EIGA) for additive manufacturing of biomedical implants

This study demonstrated the viability of the electrode induction gas atomization process (EIGA) to produce spherical Ti-5Fe powder suitable for additive manufacturing. The resulting powder is spherical and presents no surface defects. Additionally, the iron distribution throughout the microstructure is homogenous and indicates similar particle size distribution and oxygen pick-up as the conventional Ti-6Al-4V titanium alloy, thus demonstrating that the Ti-5Fe can achieve equal atomization behavior and powder outcome. The results of the study show how EIGA-type gas atomization can be an efficient scale-up route to produce Ti-5Fe low-cost titanium alloy powder for additive manufacturing, which offers a broader perspective into biomaterial application.

Effect of TIG-Welding on the Structure and Mechanical Properties of Low-Cost Titanium Alloy Ti-2.8Al-5.1Mo-4.9Fe Welded Joints

Titanium alloys are widely used in aerospace, automotive, biomedical and marine engineering due to their good hot and cold processing properties, fracture toughness, high specific strength and good deformability. Nevertheless, titanium is also characterized by very high production costs, which are approximately 6 times and 30 times higher, respectively, in comparison to those to obtain the same quantity of aluminum or steel relegating titanium to high demanding sectors. One possible way to reduce the cost of titanium is to use cheaper alloying elements instead of vanadium or niobium to stabilize the body-centred-cubic (B.C.C) β-phase. TIG-welding of high-strength low-cost pseudo-β titanium alloys is complicated, primarily due to the high content of alloying elements, such as iron, molybdenum, as well as the use of oxygen as an alloying elements. By the correct choice of welding modes in most cases, it is possible to obtain welded joints of high-strength pseudo-β titanium alloys with good microstructure and mechanical properties. To study the influence of TIG welding on the structure and mechanical properties of low-cost titanium alloy Ti–2.8Al–5.1Mo–4.9Fe, two types of TIG-welding chosen: standard fusion TIG welding and TIG welding on the thin flux layer.

Simultaneously improved strength and ductility of low-cost Ti-Al-V-Fe alloy with TiB2 addition and thermomechanical processing

To obtain the low-cost titanium alloys with simultaneously improved strength and ductility by thermomechanical processing, 0.1 wt% of boron was added to the Ti-4Al-2.5V-1.5Fe alloy using titanium diboride (TiB2) as a boron source. The deformation mechanisms and microstructure evolution were systematically studied by comparative investigation of Ti-4Al-2.5V-1.5Fe alloys with and without boron. The results indicated that the addition of boride had a significant effect on the material parameters. Furthermore, TiB greatly improved the spheroidization and recrystallization of the alloy, and it can effectively limit grain growth during thermal exposure. Consequently, both high-temperature forging and further thermal deformation facilitated the generation and retention of the fine grain structure, dramatically improving the processibility of Ti alloys. For bare alloys, severe plastic deformation often leads to inhomogeneous microstructures and flow instability, which is harmful to mechanical integrity. In contrast, the addition of borides can significantly mitigate flow localization. In this study, boron-modified titanium alloys exhibited improved processibility and beneficial mechanical properties attributed to beneficial effects due to the addition of borides, which may enable new strategies for manufacturing high-strength titanium alloys in a more cost-effective way.

Low-Cycle Fatigue Behavior and Fracture Characteristics of Low-Cost Ti-2Fe-0.1B Alloy

In recent decades, the effect of Fe element addition on titanium alloy has been investigated extensively due to the development of low-cost titanium alloys, as well as B microalloying, which could decrease the grain size of titanium alloys during the casting process. As a key structural material, the study of the fatigue behavior of titanium alloys is crucial and always attractive for scientists. Hence, in this paper, the low cycle fatigue (LCF) behavior and fracture characteristics of a low-cost Ti-2Fe-0.1B alloy with a lamellar structure were investigated systematically, five different strain amplitudes (Δεt/2) in the range from 0.6% to 1.4% were selected to control the LCF process. It was found that the Ti-2Fe-0.1B alloy exhibits continuous cyclic softening behavior in the cycle as a whole at Δεt/2 ≤ 1.2%, while at Δεt/2 = 1.4%, it exhibits slight cyclic hardening at the initial stage of the cycle, then shows cyclic softening. Compared with pure titanium and other typical titanium alloys, the Ti-2Fe-0.1B alloy indicated maximum fatigue life under the same strain amplitude, it can be attributed to the fine grain size result from the effect of Fe element and trace B, which could hinder the dislocation movement and crack propagation.

Effect of power spinning and heat treatment on microstructure evolution and mechanical properties of duplex low-cost titanium alloy

• A power spinning process and subsequent three kinds of heat-treatment routines were conducted on the new duplex Ti-5.5Al-1Fe-3.5Cr-3.2Zr-0.2Si alloy. • The microstructure evolution and mechanical properties of low-cost titanium alloy were systematically studied. • The as-spun specimens, subjected to low-temperature annealing at 550°C for a duration of less than 4 h, exhibited a good balance of strength and ductility. • The irregular variation of elongation can be ascribed to the competition of precipitation and spheroidization. The microstructural evolution and mechanical properties of low-cost Ti-5.5Al-1Fe-3.5Cr-3.2Zr-0.2Si alloy during power spinning and after three types of heat-treatment routines (low-temperature annealing, high-temperature annealing, solution and annealing) were systematically studied. An effective heat-treatment routine to fabricate high-strength and acceptable ductile as-spun Ti-5.5Al-1Fe-3.5Cr-3.2Zr-0.2Si alloy tubes was then proposed whereby the relationship between the mechanical performances and microstructures was analyzed. The {0002} α and {001} β textures were formed after multi-pass power spinning. The as-spun LC-Ti alloy exhibited a good combination of strength and elongation after heat treatment at 550 °C for 4 h, which was ascribed to the large plastic induced low-temperature spheroidization of deformed α phase and nanoscale α precipitation from deformed β phase. However, the elongation decreased evidently when Zr2Si/TiCr2 participated at the interphase boundaries after heat treatment at 550 °C for 8 h. In high-temperature annealing, the elongation changed nonlinearly owing to the precipitation of Zr2Si particles at triangular grain boundaries treated at 750 °C for 1 h, and the spheroidization of the deformed α p phase. Under solution and annealing conditions, lenticular α s would participate from the metastable β grains, which contributed to the greatest strength albeit poor ductility. This study provides an effective guidance for the processing and application of the low-cost titanium alloy.

Simulation Study on the Investment Casting Process of a Low-Cost Titanium Alloy Gearbox based on ProCAST

A model of investment casting of a titanium alloy gearbox based on the ProCAST software was established in this work, and the simulated result was used to optimize the casting process. The flow and temperature field of casting were simulated based on an actual pouring process. Casting defects and the solidification process were analyzed. The results show that the defects can be predicted by the simulation result exactly, and the simulated temperature field is in accordance with the actual process. Shrinkage and porosity are observably alleviated by remodelling the casting mould. The casting temperature field and solidification simulation results show that the casting defects arise from hot spots and heat accumulation. The temperature-time curve of different representative location nodes of casting further confirms the defect simulation results. In addition, the use of low-cost alloy elements reduces raw material costs. Compared with TC4 alloy, the mechanical properties of the casting remain unchanged.

Effect of Pre-Heating and Post-Weld Local Heat Treatment on the Microstructure and Mechanical Properties of Low-Cost β-Titanium Alloy Welding Joints, Obtained by EBW

Titanium (Ti) is highly valued for its strength-to-weight ratio and corrosion resistance. However, after it is processed to a wrought, or shaped form, it is typically in excess of 40 times more expensive than the corresponding steel part and nearly 20 times more expensive than the aluminum part. The high production costs of titanium in comparison to other structural metals is the main limiting factor for the wide employment of titanium. Cost reduction can be addressed considering creative fabrication methods and/or formulating new chemical compositions. In general, low-cost technology of titanium alloy can be implemented from raw material, alloy design and processing and forming. The core idea of low-cost titanium alloy design is to use cheap alloying elements to instead of expensive alloying elements without reducing the performance of the alloy. Iron has been considered for the development of few low-cost titanium alloys because of its stabilizing effect of the β-phase. Besides, it has a large solid solubility in β-Ti and owing to the atomic size difference with Ti can enable significant solution strengthening. But due to the high density of iron, high quantity of β-stabilizing elements and the formation of TiFe-based brittle intermetallic phases, welding joints of low-cost titanium alloys are prone to formation of cold cracks which is very important limiting factor for obtaining high quality welded joints with a strength of at least 90% compared to the strength of base material. Electron Beam Welding with its higher welding speed and intensity, can prevent formation of intermetallic and could help in obtaining welds with better mechanical properties, especially in combination with either pre-or post-welding heat treatment. The aim of this work is to study the effect of pre-heating and post-welding heat treatment on low-cost β-titanium alloy Ti-2.8Al-5.1Mo-4.9Fe welding joints by performing electron beam welding in combination with pre-and post-welding heat treatment. Specifically, this work will help to understand the influence of such techniques on the structure, phase composition and mechanical properties of low-cost β-titanium alloy welded joint.

Effect of Electron Beam Welding on the Microstructure and Mechanical Properties of Low-Cost Titanium Alloys

An expansion of titanium to mass production industries, such as the automotive, is prevented by its high extraction and production costs (e.g. extraction of titanium from its ores is 15 times and 3 times higher than that of iron and aluminum, respectively). One possible way to reduce the cost of titanium is to use cheaper alloying elements instead of vanadium or niobium to stabilize the body-centered-cubic β-phase. Iron has been considered for the development of few low-cost titanium alloys, such as the Ti–2.8Al–5.1Mo–4.9Fe, Ti-1.5Al-6.3Mo-4.4Fe and Ti-3.6Fe-0.25O alloys, because of its stabilizing effect of the β-phase. Nevertheless, due to the high density of iron, high quantity of β-stabilizing elements and the formation of TiFe-based brittle intermetallic phases, welding joints of low-cost titanium alloys are prone to formation of cold cracks which is very important limiting factor for obtaining welded joints with a strength of at least 90% compared to the strength of base material. Electron Beam Welding with its higher welding speed and intensity used in the process has its advantages over other welding methods in achieving the higher temperature required for melting and joining titanium alloys and obtaining welds with better mechanical properties. In this work the influence of the electron beam welding thermal cycle on the structure and mechanical properties of low-cost titanium alloys Ti–2.8Al–5.1Mo–4.9Fe, Ti-1.5Al-6.3Mo-4.4Fe and Ti-3.6Fe-0.25O will be studied.

Mapping of microstructure features and micromechanical properties of Ti–xAl–yFe (x=0–6, y=4–10 wt.%) alloys via diffusion couple method

In this work, a diffusion couple of Ti–6Al–4Fe/Ti–10Fe (wt. %) was fabricated and heat-treated under BASCA (β-annealing, slow cooling, and aging) processing conditions to facilitate the strengthening and toughening design for low-cost titanium alloys. Assisted by Scanning Electron Microscopy (SEM), Electron Probe Micro analyses (EPMA), and nanoindentation, a picture was constructed to map the composition-dependent microstructure features and micromechanical properties in the composition array of Ti–(0–6)Al–(10–4)Fe (wt. %). The reduction of Al and the enrichment of Fe resulted in the α lamellae in finer appearance and less amount, indicating that the alloys with the same chemical composition as that in the micro-areas would show similar microstructure features. The elastic modulus E obtained from nanoindentation exhibited a decreasing trend with Al impoverishment which was in contrast to a slight increase of nanohardness H. The measured elastic modulus and nanohardness enabled evaluations of wear resistance (H/E), resistance to plastic deformation (H3/E2), elastic recovery rate (Ue/Ut), and plasticity index (Up/Ut) in the micro-areas which served as the property indices analogous to those of the independent alloys with the same chemical compositions. The indices varied monotonously in the composition array. The highest H/E, H3/E2, Ue/Ut and the lowest Up/Ut was discovered at Ti–10Fe terminal, indicating good wear resistance and longer service potentials. Nevertheless, the high modulus E = 145.76 GPa of Ti–4.96Al–4.43Fe is promising in the ballistic application.

Influence of TIG Welding Thermal Cycle on Temperature Distribution and Phase Transformation in Low-cost Titanium Alloy

Low-cost β-phase titanium alloys are starting to get a lot of attention and application in aircraft and mechanical engineering. They are effectively hardened by heat treatment and have a strength 10-20% higher than α-alloys. However, during TIG welding of low-cost titanium alloys, difficulties arise due to a change in the structure and the formation of metastable phases in the welded joint. The main criterion for choosing the modes of TIG welding is the optimal interval of the cooling rate in the weld, therefore it is advisable to compare different modes of TIG welding, including the use of pre-heating, by their thermal effect on the weld metal and the heat-affected zone.

Predicting Workability of a Low-Cost Powder Metallurgical Ti-5Al-2Fe-3Mo Alloy Using Constitutive Modeling and Processing Map.

A low-cost titanium alloy (Ti–5Al–2Fe–3Mo wt.%) was designed and fabricated by blended elemental powder metallurgy (BEPM) process. The high-temperature deformation behavior of the powder metallurgical Ti–5Al–2Fe–3Mo wt.% (PM-TiAlFeMo) alloy was investigated by hot compression tests at temperatures ranging from 700 to 1000 °C and strain rates ranging from 0.001 to 10 s−1. The flow curves were employed to develop the Arrhenius-type constitutive model in consideration of effects of deformation temperature, strain rate, and flow stress. The value of activation energy (Q) was determined as 413.25 kJ/mol. In order to describe the workability and predict the optimum hot processing parameters of the PM-TiAlFeMo alloy, the processing map has been established based on the true stress–true strain curves and power dissipation efficiency map. Moreover, microstructure observations match well with the analyses about deformation mechanisms, revealing that dynamic recovery and dynamic recrystallization are dominant softening mechanisms at relatively high temperatures. However, the kinking and breaking of microstructure prefer to occur at relatively low temperatures.

Impact of Equal Channel Angular Pressing on Mechanical Behavior and Corrosion Resistance of Hot-Rolled Ti-2Fe-0.1B Alloy.

In the present study, the unique bimodal grain size distribution microstructure with the ultrafine substrate and embedded macro grains was fabricated by a traditional hot-rolling process in a novel low-cost Ti-2Fe-0.1B titanium alloy, which possesses a good combination of strength (around 663 MPa) and ductility (around 30%) without any post heat treatment. Meanwhile, the mechanical behavior and corrosion resistance of hot-rolled Ti-2Fe-0.1B alloy after equal channel angular pressing (ECAP) deformation were studied. Results indicated that the average grain size decreased to 0.24 μm after 4 passes ECAP deformation, which led to the enhancement of tensile strength to around 854 MPa and good ductility to around 15%. In addition, corrosion resistance was also improved after ECAP due to the rapid self-repairing and thicker passivation film. Our study revealed that the novel low-cost titanium alloy after hot-rolling and ECAP could be used instead of Ti-6Al-4V in some industrial applications due to similar mechanical behavior and better corrosion resistance.

Development of low-cost titanium alloys: A chronicle of challenges and opportunities

The production of titanium alloys became fully commercialized in the 1950s and that was precisely 145 years since titanium ores, ilmenite and rutile were first discovered. In the 2000s, up to 100 titanium alloys of different grades were already designed, but only 20% of these alloys are in use on a commercial scale. Despite this, there is growing interest in the design of new titanium alloys owing to the global demand for stronger, lighter and less-expensive alloys for engineering applications. This paper presents an overview of the different design strategies that were adopted in producing low-cost titanium alloys since the alloys already met two important demands, strength and lightweight. Some of the challenges and opportunities that are associated with these strategies are mentioned.

Oxidation and Corrosion Behavior of New Low-Cost Ti-7Fe-3Al and Ti-7Fe-5Cr Alloys from Titanium Hydride Powders

High production costs of Ti alloys usually hinders their use in industry sectors like the automotive and hence, low-cost titanium alloys could broaden titanium alloy usage. This work presents the study of three alloys— Ti-Fe, Ti-Fe-Al, and Ti-Fe-Cr—produced by powder metallurgy methods. The design of the compositions was aimed at reducing cost and enhance the oxidation and corrosion resistance while not decreasing the mechanical performance. The use of titanium hydride as raw material instead of Ti powder is highlighted as a key feature in the design and manufacturing procedure of the alloys. Introducing a dehydrogenation process during sintering favors the densification process while reducing the oxygen contamination and the production cost. There is a lack of studies focused on the implementation of affordable PM Ti alloys in high demanding environments. Therefore, a study of high temperature oxidation resistance and electrochemical behavior was performed.

Research and Development of Low-cost Titanium Alloys

Excellent mechanical properties combined with low density, good corrosion resistance and welding, make titanium alloy attractive structural materials for aerospace, ship navigation, weaponry and nuclear industry. However, the high cost impedes the further use of titanium alloy in different fields, and which is the key factor for productivity and further use of titanium alloy. Aiming at lost cost of titanium alloy, three parts of raw material, alloy design and working forming were overviewed, which will offer reference for how to low cost of titanium alloy.

Influence of microstructure on the fatigue behavior of blended elemental Ti-6AL-4V alloy post-consolidated by extrusion

The blended elemental (BE) route is currently the main way for obtaining cost-affordable titanium alloys. Via post-consolidation processes like hot isostatic pressing (HIP) or thermomechanical processing, the material can improve its mechanical properties. In this work, a titanium alloy is processed via the BE approach, combined with thermomechanical processing of the sintered billets and subsequently heat treated. The tensile behavior of the sintered, extruded and heat-treated Ti-6Al-4V alloy was studied, finding an overall improvement of the properties after extrusion and a considerable increase in strength without compromising ductility after heat treatment. The high cycle fatigue behavior of the as-extruded alloy was studied by means of axial testing. There is a strong dependence between the location of the initiation of failure of the alloy and its fatigue life, but the defects that initiated failure were facets, not pores. The fatigue life of the as-extruded alloy is comparable to that of other fully-dense powder metallurgy (PM) and wrought Ti-6Al-4V alloys. These findings encourage the use of this route of processing as a balanced approach between low-cost and high-performance titanium alloys.