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Titanium alloys

March 02, 2023

Titanium alloys are alloys that contain a mixture of titanium and other chemical elements. Such alloys have very high tensile strength and toughness (even at extreme temperatures). They are light in weight, have extraordinary corrosion resistance and the ability to withstand extreme temperatures. However, the high cost of both raw materials and processing limit their use to military applications, aircraft, spacecraft, bicycles, medical devices, jewelry, highly stressed components such as connecting rods on expensive sports cars and some premium sports equipment and consumer electronics.

Although "commercially pure" titanium has acceptable mechanical properties and has been used for orthopedic and dental implants, for most applications titanium is alloyed with small amounts of aluminium and vanadium, typically 6% and 4% respectively, by weight. This mixture has a solid solubility which varies dramatically with temperature, allowing it to undergo precipitation strengthening. This heat treatment process is carried out after the alloy has been worked into its final shape but before it is put to use, allowing much easier fabrication of a high-strength product.

Categories

Titanium alloys are generally classified into four main categories:[1]

  • Alpha alloys which contain neutral alloying elements (such as tin) and/ or alpha stabilisers (such as aluminium or oxygen) only. These are not heat treatable. Examples include:[2] Ti-5Al-2Sn-ELI, Ti-8Al-1Mo-1V.
  • Near-alpha alloys contain small amount of ductile beta-phase. Besides alpha-phase stabilisers, near-alpha alloys are alloyed with 1–2% of beta phase stabilizers such as molybdenum, silicon or vanadium. Examples include:[2] Ti-6Al-2Sn-4Zr-2Mo, Ti-5Al-5Sn-2Zr-2Mo, IMI 685, Ti 1100.
  • Alpha and beta alloys, which are metastable and generally include some combination of both alpha and beta stabilisers, and which can be heat treated. Examples include:[2] Ti-6Al-4V, Ti-6Al-4V-ELI, Ti-6Al-6V-2Sn, Ti-6Al-7Nb.
  • Beta and near beta alloys, which are metastable and which contain sufficient beta stabilisers (such as molybdenum, silicon and vanadium) to allow them to maintain the beta phase when quenched, and which can also be solution treated and aged to improve strength. Examples include:[2] Ti-10V-2Fe-3Al, Ti–29Nb–13Ta–4.6Zr,[3] Ti-13V-11Cr-3Al, Ti-8Mo-8V-2Fe-3Al, Beta C, Ti-15-3.

Beta-titanium

Beta titanium alloys exhibit the BCC allotropic form of titanium (called beta). Elements used in this alloy are one or more of the following other than titanium in varying amounts. These are molybdenum, vanadium, niobium, tantalum, zirconium, manganese, iron, chromium, cobalt, nickel, and copper.

The titanium alloys have excellent formability and can be easily welded.[4]

Beta titanium is nowadays largely utilized in the orthodontic field and was adopted for orthodontics use in the 1980s. This type of alloy replaced stainless steel for certain uses, as stainless steel had dominated orthodontics since the 1960s. It has strength/modulus of elasticity ratios almost twice those of 18-8 austenitic stainless steel, larger elastic deflections in springs, and reduced force per unit displacement 2.2 times below those of stainless steel appliances.

Some of the beta titanium alloys can convert to hard and brittle hexagonal omega-titanium at cryogenic temperatures[5] or under influence of ionizing radiation.[6]

Transition temperature

The crystal structure of titanium at ambient temperature and pressure is close-packed hexagonal α phase with a c/a ratio of 1.587. At about 890 °C, the titanium undergoes an allotropic transformation to a body-centred cubic β phase which remains stable to the melting temperature.

Some alloying elements, called alpha stabilizers, raise the alpha-to-beta transition temperature,[i] while others (beta stabilizers) lower the transition temperature. Aluminium, gallium, germanium, carbon, oxygen and nitrogen are alpha stabilizers. Molybdenum, vanadium, tantalum, niobium, manganese, iron, chromium, cobalt, nickel, copper and silicon are beta stabilizers.[7]

Properties

Generally, beta-phase titanium is the more ductile phase and alpha-phase is stronger yet less ductile, due to the larger number of slip planes in the bcc structure of the beta-phase in comparison to the hcp alpha-phase. Alpha-beta-phase titanium has a mechanical property which is in between both.

Titanium dioxide dissolves in the metal at high temperatures, and its formation is very energetic. These two factors mean that all titanium except the most carefully purified has a significant amount of dissolved oxygen, and so may be considered a Ti–O alloy. Oxide precipitates offer some strength (as discussed above), but are not very responsive to heat treatment and can substantially decrease the alloy's toughness.

Many alloys also contain titanium as a minor additive, but since alloys are usually categorized according to which element forms the majority of the material, these are not usually considered to be "titanium alloys" as such. See the sub-article on titanium applications.

Titanium alone is a strong, light metal. It is stronger than common, low-carbon steels, but 45% lighter. It is also twice as strong as weak aluminium alloys but only 60% heavier. Titanium has outstanding corrosion resistance to seawater, and thus is used in propeller shafts, rigging and other parts of boats that are exposed to seawater. Titanium and its alloys are used in airplanes, missiles, and rockets where strength, low weight, and resistance to high temperatures are important. Further, since titanium does not react within the human body, it and its alloys are used in artificial joints, screws, and plates for fractures, and for other biological implants. See: Titanium orthopedic implants.

Titanium grades

The ASTM International standard on titanium and titanium alloy seamless pipe references the following alloys, requiring the following treatment:

"Alloys may be supplied in the following conditions: Grades 5, 23, 24, 25, 29, 35, or 36 annealed or aged; Grades 9, 18, 28, or 38 cold-worked and stress-relieved or annealed; Grades 9, 18, 23, 28, or 29 transformed-beta condition; and Grades 19, 20, or 21 solution-treated or solution-treated and aged."[8]

"Note 1—H grade material is identical to the corresponding numeric grade (that is, Grade 2H = Grade 2) except for the higher guaranteed minimum UTS, and may always be certified as meeting the requirements of its corresponding numeric grade. Grades 2H, 7H, 16H, and 26H are intended primarily for pressure vessel use."[8]

"The H grades were added in response to a user association request based on its study of over 5200 commercial Grade 2, 7, 16, and 26 test reports, where over 99% met the 58 ksi minimum UTS."[8]

Grade 1
is the most ductile and softest titanium alloy. It is a good solution for cold forming and corrosive environments. ASTM/ASME SB-265 provides the standards for commercially pure titanium sheet and plate.[9]
Grade 2
Unalloyed titanium, standard oxygen.
Grade 2H
Unalloyed titanium (Grade 2 with 58 ksi minimum UTS).
Grade 3
Unalloyed titanium, medium oxygen.
Grades 1-4 are unalloyed and considered commercially pure or "CP". Generally the tensile and yield strength goes up with grade number for these "pure" grades. The difference in their physical properties is primarily due to the quantity of interstitial elements. They are used for corrosion resistance applications where cost, ease of fabrication, and welding are important.
Grade 5 also known as Ti6Al4V, Ti-6Al-4V or Ti 6-4
not to be confused with Ti-6Al-4V-ELI (Grade 23), is the most commonly used alloy. It has a chemical composition of 6% aluminum, 4% vanadium, 0.25% (maximum) iron, 0.2% (maximum) oxygen, and the remainder titanium.[10] It is significantly stronger than commercially pure titanium (grades 1-4) while having the same stiffness and thermal properties (excluding thermal conductivity, which is about 60% lower in Grade 5 Ti than in CP Ti).[11] Among its many advantages, it is heat treatable. This grade is an excellent combination of strength, corrosion resistance, weld and fabricability.

"This alpha-beta alloy is the workhorse alloy of the titanium industry. The alloy is fully heat treatable in section sizes up to 15 mm and is used up to approximately 400 °C (750 °F). Since it is the most commonly used alloy – over 70% of all alloy grades melted are a sub-grade of Ti6Al4V, its uses span many aerospace airframe and engine component uses and also major non-aerospace applications in the marine, offshore and power generation industries in particular."[12]

"Applications: Blades, discs, rings, airframes, fasteners, components. Vessels, cases, hubs, forgings. Biomedical implants."[10]

Generally, Ti-6Al-4V is used in applications up to 400 degrees Celsius. It has a density of roughly 4420 kg/m3, Young's modulus of 120 GPa, and tensile strength of 1000 MPa.[13] By comparison, annealed type 316 stainless steel has a density of 8000 kg/m3, modulus of 193 GPa, and tensile strength of 570 MPa.[14] Tempered 6061 aluminium alloy has a density of 2700 kg/m3, modulus of 69 GPa, and tensile strength of 310 MPa, respectively.[15]
Ti-6Al-4V standard specifications include:[16]
  • AMS: 4911, 4928, 4965, 4967, 6930, 6931, T-9046, T9047
  • ASTM: B265, B348, F1472
  • MIL: T9046 T9047
  • DMS: 1592, 1570
Grade 6
contains 5% aluminium and 2.5% tin. It is also known as Ti-5Al-2.5Sn. This alloy is used in airframes and jet engines due to its good weldability, stability and strength at elevated temperatures.[17]
Grade 7
contains 0.12 to 0.25% palladium. This grade is similar to Grade 2. The small quantity of palladium added gives it enhanced crevice corrosion resistance at low temperatures and high pH.[18]
Grade 7H
is identical to Grade 7 with enhanced corrosion resistance.[18]
Grade 9
contains 3.0% aluminium and 2.5% vanadium. This grade is a compromise between the ease of welding and manufacturing of the "pure" grades and the high strength of Grade 5. It is commonly used in aircraft tubing for hydraulics and in athletic equipment.
Grade 11
contains 0.12 to 0.25% palladium. This grade has enhanced corrosion resistance.[19]
Grade 12
contains 0.3% molybdenum and 0.8% nickel.[19]
Grades 13, 14, and 15
all contain 0.5% nickel and 0.05% ruthenium.
Grade 16
contains 0.04 to 0.08% palladium. This grade has enhanced corrosion resistance.
Grade 16H
contains 0.04 to 0.08% palladium.
Grade 17
contains 0.04 to 0.08% palladium. This grade has enhanced corrosion resistance.[citation needed]
Grade 18
contains 3% aluminium, 2.5% vanadium and 0.04 to 0.08% palladium. This grade is identical to Grade 9 in terms of mechanical characteristics. The added palladium gives it increased corrosion resistance.[citation needed]
Grade 19
contains 3% aluminium, 8% vanadium, 6% chromium, 4% zirconium, and 4% molybdenum.
Grade 20
contains 3% aluminium, 8% vanadium, 6% chromium, 4% zirconium, 4% molybdenum and 0.04% to 0.08% palladium.
Grade 21
contains 15% molybdenum, 3% aluminium, 2.7% niobium, and 0.25% silicon.
Grade 23 also known as Ti-6Al-4V-ELI or TAV-ELI
contains 6% aluminium, 4% vanadium, 0.13% (maximum) Oxygen. ELI stands for Extra Low Interstitial. Reduced interstitial elements oxygen and iron improve ductility and fracture toughness with some reduction in strength.[19] TAV-ELI is the most commonly used medical implant-grade titanium alloy.[19][20]
Ti-6Al-4V-ELI standard specifications include:[20]
  • AMS: 4907, 4930, 6932, T9046, T9047
  • ASTM: B265, B348, F136
  • MIL: T9046 T9047
Grade 24
contains 6% aluminium, 4% vanadium and 0.04% to 0.08% palladium.
Grade 25
contains 6% aluminium, 4% vanadium and 0.3% to 0.8% nickel and 0.04% to 0.08% palladium.
Grades 26, 26H, and 27
all contain 0.08 to 0.14% ruthenium.
Grade 28
contains 3% aluminium, 2.5% vanadium and 0.08 to 0.14% ruthenium.
Grade 29
contains 6% aluminium, 4% vanadium and 0.08 to 0.14% ruthenium.
Grades 30 and 31
contain 0.3% cobalt and 0.05% palladium.
Grade 32
contains 5% aluminium, 1% tin, 1% zirconium, 1% vanadium, and 0.8% molybdenum.
Grades 33 and 34
contain 0.4% nickel, 0.015% palladium, 0.025% ruthenium, and 0.15% chromium .[citation needed]
Grade 35
contains 4.5% aluminium, 2% molybdenum, 1.6% vanadium, 0.5% iron, and 0.3% silicon.
Grade 36
contains 45% niobium.
Grade 37
contains 1.5% aluminium.
Grade 38
contains 4% aluminium, 2.5% vanadium, and 1.5% iron. This grade was developed in the 1990s for use as an armor plating. The iron reduces the amount of Vanadium needed as a beta stabilizer. Its mechanical properties are very similar to Grade 5, but has good cold workability similar to grade 9.[21]

Heat treatment

Titanium alloys are heat treated for a number of reasons, the main ones being to increase strength by solution treatment and aging as well as to optimize special properties, such as fracture toughness, fatigue strength and high temperature creep strength.

Alpha and near-alpha alloys cannot be dramatically changed by heat treatment. Stress relief and annealing are the processes that can be employed for this class of titanium alloys. The heat treatment cycles for beta alloys differ significantly from those for the alpha and alpha-beta alloys. Beta alloys can not only be stress relieved or annealed, but also can be solution treated and aged. The alpha-beta alloys are two-phase alloys, comprising both alpha and beta phases at room temperature. Phase compositions, sizes, and distributions of phases in alpha-beta alloys can be manipulated within certain limits by heat treatment, thus permitting tailoring of properties.

Alpha and near-alpha alloys
The micro-structure of alpha alloys cannot be strongly manipulated by heat treatment since alpha alloys undergo no significant phase change. As a result, high strength can not be acquired for the alpha alloys by heat treatment. Yet, alpha and near-alpha titanium alloys can be stress relieved and annealed.
Alpha-beta alloys
By working as well as heat treatment of alpha-beta alloys below or above the alpha-beta transition temperature, large micro-structural changes can be achieved. This may give a substantial hardening of the material. Solution treatment plus aging is used to produce maximum strengths in alpha-beta alloys. Also, other heat treatments, including stress-relief heat treatments, are practiced for this group of titanium alloys as well.
Beta alloys
In commercial beta alloys, stress-relieving and aging treatments can be combined.

Applications

Aerospace structures

Titanium is used regularly in aviation for its resistance to corrosion and heat, and its high strength-to-weight ratio. Titanium alloys are generally stronger than aluminium alloys, while being lighter than steel.

Biomedical

 
Titanium plate for wrist

Titanium alloys have been extensively used for the manufacturing of metal orthopedic joint replacements and bone plate surgeries. They are normally produced from wrought or cast bar stock by CNC, CAD-driven machining, or powder metallurgy production. Each of these techniques comes with inherent advantages and disadvantages. Wrought products come with an extensive material loss during machining into the final shape of the product and for cast samples the acquirement of a product in its final shape somewhat limits further processing and treatment (e.g. precipitation hardening), yet casting is more material effective. Traditional powder metallurgy methods are also more material efficient, yet acquiring fully dense products can be a common issue.[22]

With the emergence of solid freeform fabrication (3D printing) the possibility to produce custom-designed biomedical implants (e.g. hip joints) has been realized. While it is not applied currently on a larger scale, freeform fabrication methods offers the ability to recycle waste powder (from the manufacturing process) and makes for selectivity tailoring desirable properties and thus the performance of the implant. Electron Beam Melting (EBM) and Selective Laser Melting (SLM) are two methods applicable for freeform fabrication of Ti-alloys. Manufacturing parameters greatly influence the microstructure of the product, where e.g. a fast cooling rate in combination with low degree of melting in SLM leads to the predominant formation of martensitic alpha-prime phase, giving a very hard product.[22]

Ti-6Al-4V / Ti-6Al-4V-ELI
This alloy has good biocompatibility, and is neither cytotoxic nor genotoxic.[23] Ti-6Al-4V suffers from poor shear strength and poor surface wear properties in certain loading conditions:[10]

Bio compatibility: Excellent, especially when direct contact with tissue or bone is required. Ti-6Al-4V's poor shear strength makes it undesirable for bone screws or plates. It also has poor surface wear properties and tends to seize when in sliding contact with itself and other metals. Surface treatments such as nitriding and oxidizing can improve the surface wear properties.[10]

Ti-6Al-7Nb
This alloy was developed as a biomedical replacement for Ti-6Al-4V, because Ti-6Al-4V contains vanadium, an element that has demonstrated cytotoxic outcomes when isolated.[24]: 1  Ti-6Al-7Nb contains 6% aluminium and 7% niobium.[24]: 18 

Ti6Al7Nb is a dedicated high strength titanium alloy with excellent biocompatibility for surgical implants. Used for replacement hip joints, it has been in clinical use since early 1986.[25]

References

Notes
  1. ^ In a titanium or titanium alloy, alpha-to-beta transition temperature is the temperature above which the beta phase becomes thermodynamically favorable.
Sources
  1. ^ Characteristics of Alpha, Alpha Beta and Beta Titanium Alloys
  2. ^ a b c d Titanium – A Technical Guide. ASM International. 2000. ISBN 9781615030620.
  3. ^ Najdahmadi, A.; Zarei-Hanzaki, A.; Farghadani, E. (1 February 2014). "Mechanical properties enhancement in Ti–29Nb–13Ta–4.6Zr alloy via heat treatment with no detrimental effect on its biocompatibility". Materials & Design. 54: 786–791. doi:10.1016/j.matdes.2013.09.007. ISSN 0261-3069.
  4. ^ Goldberg, Jon; Burstone, Charles J. (1979). "An Evaluation of Beta Titanium Alloys for Use in Orthodontic Appliances". Journal of Dental Research. 58 (2): 593–599. doi:10.1177/00220345790580020901. PMID 283089. S2CID 29064479.
  5. ^ De Fontaine§§, D.; Paton, N.E.; Williams, J.C. (November 1971). "Transformation de la phase omega dans les alliages de titane comme exemple de reactions controlees par deplacementDie omega-phasenumwandlung in titanlegierungen als beispiel einer verschiebungskontrollierten reaktion". Acta Metallurgica. 19 (11): 1153–1162. doi:10.1016/0001-6160(71)90047-2. Retrieved 27 April 2020.
  6. ^ Ishida, Taku; Wakai, Eiichi; Makimura, Shunsuke; Casella, Andrew M.; Edwards, Danny J.; Senor, David J.; Ammigan, Kavin; Hurh, Patrick G.; Densham, Christopher J.; Fitton, Michael D.; Bennett, Joe M.; Kim, Dohyun; Simos, Nikolaos; Hagiwara, Masayuki; Kawamura, Naritoshi; Meigo, Shin-ichiro; Yohehara, Katsuya (2020). "Tensile behavior of dual-phase titanium alloys under high-intensity proton beam exposure: Radiation-induced omega phase transformation in Ti-6Al-4V". Journal of Nuclear Materials. 541: 152413. arXiv:2004.11562. doi:10.1016/j.jnucmat.2020.152413. S2CID 216144772.
  7. ^ Vydehi Arun Joshi. Titanium Alloys: An Atlas of Structures and Fracture Features. CRC Press, 2006.
  8. ^ a b c ASTM B861 – 10 Standard Specification for Titanium and Titanium Alloy Seamless Pipe (Grades 1 to 38)
  9. ^ Titanium Grades, Application
  10. ^ a b c d "Titanium-6-4". Retrieved 2009-02-19.
  11. ^ Compare Materials: Commercially Pure Titanium and 6Al-4V (Grade 5) Titanium
  12. ^ Titanium Alloys – Ti6Al4V Grade 5
  13. ^ Material Properties Data: 6Al-4V (Grade 5) Titanium Alloy
  14. ^ Material Properties Data: Marine Grade Stainless Steel
  15. ^ Material Properties Data: 6061-T6 Aluminum
  16. ^ "6Al-4V Titanium". Performance Titanium Group.
  17. ^ "Titanium Ti-5Al-2.5Sn (Grade 6) - Material Web".
  18. ^ a b . Archived from the original on 2012-04-26. Retrieved 2011-12-19.
  19. ^ a b c d Titanium Grade Overview
  20. ^ a b "6Al-4V-ELI Titanium". Performance Titanium Group.
  21. ^ ArmyCorrosion.com[dead link]
  22. ^ a b Murr, L. E.; Quinones, S. A.; Gaytan, S. M.; Lopez, M. I.; Rodela, A.; Martinez, E. Y.; Hernandez, D. H.; Martinez, E.; Medina, F. (2009-01-01). "Microstructure and mechanical behavior of Ti–6Al–4V produced by rapid-layer manufacturing, for biomedical applications". Journal of the Mechanical Behavior of Biomedical Materials. 2 (1): 20–32. doi:10.1016/j.jmbbm.2008.05.004. PMID 19627804.
  23. ^ Velasco-Ortega, E (Sep 2010). "In vitro evaluation of cytotoxicity and genotoxicity of a commercial titanium alloy for dental implantology". Mutat. Res. 702 (1): 17–23. doi:10.1016/j.mrgentox.2010.06.013. PMID 20615479.
  24. ^ a b The fatigue resistance of commercially pure titanium(grade II), titanium alloy (Ti6Al7Nb) and conventional cobalt-chromium cast clasps by Mali Palanuwech; Inaugural-Dissertation zur Erlangung des Doktorgrades der Zahnheilkunde der Medizinschen Fakultät der Eberhard-Karls-Universität zu Tübingenvorgelegt; Munich (2003). Retrieved 8 September 2012
  25. ^ Titanium Alloys – Ti6Al7Nb Properties and Applications. Retrieved 8 September 2012

External links

 
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March 02, 2023
titanium, alloys, alloys, that, contain, mixture, titanium, other, chemical, elements, such, alloys, have, very, high, tensile, strength, toughness, even, extreme, temperatures, they, light, weight, have, extraordinary, corrosion, resistance, ability, withstan. Titanium alloys are alloys that contain a mixture of titanium and other chemical elements Such alloys have very high tensile strength and toughness even at extreme temperatures They are light in weight have extraordinary corrosion resistance and the ability to withstand extreme temperatures However the high cost of both raw materials and processing limit their use to military applications aircraft spacecraft bicycles medical devices jewelry highly stressed components such as connecting rods on expensive sports cars and some premium sports equipment and consumer electronics Although commercially pure titanium has acceptable mechanical properties and has been used for orthopedic and dental implants for most applications titanium is alloyed with small amounts of aluminium and vanadium typically 6 and 4 respectively by weight This mixture has a solid solubility which varies dramatically with temperature allowing it to undergo precipitation strengthening This heat treatment process is carried out after the alloy has been worked into its final shape but before it is put to use allowing much easier fabrication of a high strength product Contents 1 Categories 2 Beta titanium 3 Transition temperature 4 Properties 5 Titanium grades 6 Heat treatment 7 Applications 7 1 Aerospace structures 7 2 Biomedical 8 References 9 External linksCategories EditTitanium alloys are generally classified into four main categories 1 Alpha alloys which contain neutral alloying elements such as tin and or alpha stabilisers such as aluminium or oxygen only These are not heat treatable Examples include 2 Ti 5Al 2Sn ELI Ti 8Al 1Mo 1V Near alpha alloys contain small amount of ductile beta phase Besides alpha phase stabilisers near alpha alloys are alloyed with 1 2 of beta phase stabilizers such as molybdenum silicon or vanadium Examples include 2 Ti 6Al 2Sn 4Zr 2Mo Ti 5Al 5Sn 2Zr 2Mo IMI 685 Ti 1100 Alpha and beta alloys which are metastable and generally include some combination of both alpha and beta stabilisers and which can be heat treated Examples include 2 Ti 6Al 4V Ti 6Al 4V ELI Ti 6Al 6V 2Sn Ti 6Al 7Nb Beta and near beta alloys which are metastable and which contain sufficient beta stabilisers such as molybdenum silicon and vanadium to allow them to maintain the beta phase when quenched and which can also be solution treated and aged to improve strength Examples include 2 Ti 10V 2Fe 3Al Ti 29Nb 13Ta 4 6Zr 3 Ti 13V 11Cr 3Al Ti 8Mo 8V 2Fe 3Al Beta C Ti 15 3 Beta titanium EditBeta titanium alloys exhibit the BCC allotropic form of titanium called beta Elements used in this alloy are one or more of the following other than titanium in varying amounts These are molybdenum vanadium niobium tantalum zirconium manganese iron chromium cobalt nickel and copper The titanium alloys have excellent formability and can be easily welded 4 Beta titanium is nowadays largely utilized in the orthodontic field and was adopted for orthodontics use in the 1980s This type of alloy replaced stainless steel for certain uses as stainless steel had dominated orthodontics since the 1960s It has strength modulus of elasticity ratios almost twice those of 18 8 austenitic stainless steel larger elastic deflections in springs and reduced force per unit displacement 2 2 times below those of stainless steel appliances Some of the beta titanium alloys can convert to hard and brittle hexagonal omega titanium at cryogenic temperatures 5 or under influence of ionizing radiation 6 Transition temperature EditThe crystal structure of titanium at ambient temperature and pressure is close packed hexagonal a phase with a c a ratio of 1 587 At about 890 C the titanium undergoes an allotropic transformation to a body centred cubic b phase which remains stable to the melting temperature Some alloying elements called alpha stabilizers raise the alpha to beta transition temperature i while others beta stabilizers lower the transition temperature Aluminium gallium germanium carbon oxygen and nitrogen are alpha stabilizers Molybdenum vanadium tantalum niobium manganese iron chromium cobalt nickel copper and silicon are beta stabilizers 7 Properties EditGenerally beta phase titanium is the more ductile phase and alpha phase is stronger yet less ductile due to the larger number of slip planes in the bcc structure of the beta phase in comparison to the hcp alpha phase Alpha beta phase titanium has a mechanical property which is in between both Titanium dioxide dissolves in the metal at high temperatures and its formation is very energetic These two factors mean that all titanium except the most carefully purified has a significant amount of dissolved oxygen and so may be considered a Ti O alloy Oxide precipitates offer some strength as discussed above but are not very responsive to heat treatment and can substantially decrease the alloy s toughness Many alloys also contain titanium as a minor additive but since alloys are usually categorized according to which element forms the majority of the material these are not usually considered to be titanium alloys as such See the sub article on titanium applications Titanium alone is a strong light metal It is stronger than common low carbon steels but 45 lighter It is also twice as strong as weak aluminium alloys but only 60 heavier Titanium has outstanding corrosion resistance to seawater and thus is used in propeller shafts rigging and other parts of boats that are exposed to seawater Titanium and its alloys are used in airplanes missiles and rockets where strength low weight and resistance to high temperatures are important Further since titanium does not react within the human body it and its alloys are used in artificial joints screws and plates for fractures and for other biological implants See Titanium orthopedic implants Titanium grades EditThe ASTM International standard on titanium and titanium alloy seamless pipe references the following alloys requiring the following treatment Alloys may be supplied in the following conditions Grades 5 23 24 25 29 35 or 36 annealed or aged Grades 9 18 28 or 38 cold worked and stress relieved or annealed Grades 9 18 23 28 or 29 transformed beta condition and Grades 19 20 or 21 solution treated or solution treated and aged 8 Note 1 H grade material is identical to the corresponding numeric grade that is Grade 2H Grade 2 except for the higher guaranteed minimum UTS and may always be certified as meeting the requirements of its corresponding numeric grade Grades 2H 7H 16H and 26H are intended primarily for pressure vessel use 8 The H grades were added in response to a user association request based on its study of over 5200 commercial Grade 2 7 16 and 26 test reports where over 99 met the 58 ksi minimum UTS 8 Grade 1 is the most ductile and softest titanium alloy It is a good solution for cold forming and corrosive environments ASTM ASME SB 265 provides the standards for commercially pure titanium sheet and plate 9 Grade 2 Unalloyed titanium standard oxygen Grade 2H Unalloyed titanium Grade 2 with 58 ksi minimum UTS Grade 3 Unalloyed titanium medium oxygen Grades 1 4 are unalloyed and considered commercially pure or CP Generally the tensile and yield strength goes up with grade number for these pure grades The difference in their physical properties is primarily due to the quantity of interstitial elements They are used for corrosion resistance applications where cost ease of fabrication and welding are important Grade 5 also known as Ti6Al4V Ti 6Al 4V or Ti 6 4 not to be confused with Ti 6Al 4V ELI Grade 23 is the most commonly used alloy It has a chemical composition of 6 aluminum 4 vanadium 0 25 maximum iron 0 2 maximum oxygen and the remainder titanium 10 It is significantly stronger than commercially pure titanium grades 1 4 while having the same stiffness and thermal properties excluding thermal conductivity which is about 60 lower in Grade 5 Ti than in CP Ti 11 Among its many advantages it is heat treatable This grade is an excellent combination of strength corrosion resistance weld and fabricability This alpha beta alloy is the workhorse alloy of the titanium industry The alloy is fully heat treatable in section sizes up to 15 mm and is used up to approximately 400 C 750 F Since it is the most commonly used alloy over 70 of all alloy grades melted are a sub grade of Ti6Al4V its uses span many aerospace airframe and engine component uses and also major non aerospace applications in the marine offshore and power generation industries in particular 12 Applications Blades discs rings airframes fasteners components Vessels cases hubs forgings Biomedical implants 10 Generally Ti 6Al 4V is used in applications up to 400 degrees Celsius It has a density of roughly 4420 kg m3 Young s modulus of 120 GPa and tensile strength of 1000 MPa 13 By comparison annealed type 316 stainless steel has a density of 8000 kg m3 modulus of 193 GPa and tensile strength of 570 MPa 14 Tempered 6061 aluminium alloy has a density of 2700 kg m3 modulus of 69 GPa and tensile strength of 310 MPa respectively 15 Ti 6Al 4V standard specifications include 16 AMS 4911 4928 4965 4967 6930 6931 T 9046 T9047 ASTM B265 B348 F1472 MIL T9046 T9047 DMS 1592 1570 dd Grade 6 contains 5 aluminium and 2 5 tin It is also known as Ti 5Al 2 5Sn This alloy is used in airframes and jet engines due to its good weldability stability and strength at elevated temperatures 17 Grade 7 contains 0 12 to 0 25 palladium This grade is similar to Grade 2 The small quantity of palladium added gives it enhanced crevice corrosion resistance at low temperatures and high pH 18 Grade 7H is identical to Grade 7 with enhanced corrosion resistance 18 Grade 9 contains 3 0 aluminium and 2 5 vanadium This grade is a compromise between the ease of welding and manufacturing of the pure grades and the high strength of Grade 5 It is commonly used in aircraft tubing for hydraulics and in athletic equipment Grade 11 contains 0 12 to 0 25 palladium This grade has enhanced corrosion resistance 19 Grade 12 contains 0 3 molybdenum and 0 8 nickel 19 Grades 13 14 and 15 all contain 0 5 nickel and 0 05 ruthenium Grade 16 contains 0 04 to 0 08 palladium This grade has enhanced corrosion resistance Grade 16H contains 0 04 to 0 08 palladium Grade 17 contains 0 04 to 0 08 palladium This grade has enhanced corrosion resistance citation needed Grade 18 contains 3 aluminium 2 5 vanadium and 0 04 to 0 08 palladium This grade is identical to Grade 9 in terms of mechanical characteristics The added palladium gives it increased corrosion resistance citation needed Grade 19 contains 3 aluminium 8 vanadium 6 chromium 4 zirconium and 4 molybdenum Grade 20 contains 3 aluminium 8 vanadium 6 chromium 4 zirconium 4 molybdenum and 0 04 to 0 08 palladium Grade 21 contains 15 molybdenum 3 aluminium 2 7 niobium and 0 25 silicon Grade 23 also known as Ti 6Al 4V ELI or TAV ELI contains 6 aluminium 4 vanadium 0 13 maximum Oxygen ELI stands for Extra Low Interstitial Reduced interstitial elements oxygen and iron improve ductility and fracture toughness with some reduction in strength 19 TAV ELI is the most commonly used medical implant grade titanium alloy 19 20 Ti 6Al 4V ELI standard specifications include 20 AMS 4907 4930 6932 T9046 T9047 ASTM B265 B348 F136 MIL T9046 T9047 dd Grade 24 contains 6 aluminium 4 vanadium and 0 04 to 0 08 palladium Grade 25 contains 6 aluminium 4 vanadium and 0 3 to 0 8 nickel and 0 04 to 0 08 palladium Grades 26 26H and 27 all contain 0 08 to 0 14 ruthenium Grade 28 contains 3 aluminium 2 5 vanadium and 0 08 to 0 14 ruthenium Grade 29 contains 6 aluminium 4 vanadium and 0 08 to 0 14 ruthenium Grades 30 and 31 contain 0 3 cobalt and 0 05 palladium Grade 32 contains 5 aluminium 1 tin 1 zirconium 1 vanadium and 0 8 molybdenum Grades 33 and 34 contain 0 4 nickel 0 015 palladium 0 025 ruthenium and 0 15 chromium citation needed Grade 35 contains 4 5 aluminium 2 molybdenum 1 6 vanadium 0 5 iron and 0 3 silicon Grade 36 contains 45 niobium Grade 37 contains 1 5 aluminium Grade 38 contains 4 aluminium 2 5 vanadium and 1 5 iron This grade was developed in the 1990s for use as an armor plating The iron reduces the amount of Vanadium needed as a beta stabilizer Its mechanical properties are very similar to Grade 5 but has good cold workability similar to grade 9 21 Heat treatment EditTitanium alloys are heat treated for a number of reasons the main ones being to increase strength by solution treatment and aging as well as to optimize special properties such as fracture toughness fatigue strength and high temperature creep strength Alpha and near alpha alloys cannot be dramatically changed by heat treatment Stress relief and annealing are the processes that can be employed for this class of titanium alloys The heat treatment cycles for beta alloys differ significantly from those for the alpha and alpha beta alloys Beta alloys can not only be stress relieved or annealed but also can be solution treated and aged The alpha beta alloys are two phase alloys comprising both alpha and beta phases at room temperature Phase compositions sizes and distributions of phases in alpha beta alloys can be manipulated within certain limits by heat treatment thus permitting tailoring of properties Alpha and near alpha alloys The micro structure of alpha alloys cannot be strongly manipulated by heat treatment since alpha alloys undergo no significant phase change As a result high strength can not be acquired for the alpha alloys by heat treatment Yet alpha and near alpha titanium alloys can be stress relieved and annealed Alpha beta alloys By working as well as heat treatment of alpha beta alloys below or above the alpha beta transition temperature large micro structural changes can be achieved This may give a substantial hardening of the material Solution treatment plus aging is used to produce maximum strengths in alpha beta alloys Also other heat treatments including stress relief heat treatments are practiced for this group of titanium alloys as well Beta alloys In commercial beta alloys stress relieving and aging treatments can be combined Applications EditAerospace structures Edit Titanium is used regularly in aviation for its resistance to corrosion and heat and its high strength to weight ratio Titanium alloys are generally stronger than aluminium alloys while being lighter than steel Biomedical Edit Titanium plate for wrist Titanium alloys have been extensively used for the manufacturing of metal orthopedic joint replacements and bone plate surgeries They are normally produced from wrought or cast bar stock by CNC CAD driven machining or powder metallurgy production Each of these techniques comes with inherent advantages and disadvantages Wrought products come with an extensive material loss during machining into the final shape of the product and for cast samples the acquirement of a product in its final shape somewhat limits further processing and treatment e g precipitation hardening yet casting is more material effective Traditional powder metallurgy methods are also more material efficient yet acquiring fully dense products can be a common issue 22 With the emergence of solid freeform fabrication 3D printing the possibility to produce custom designed biomedical implants e g hip joints has been realized While it is not applied currently on a larger scale freeform fabrication methods offers the ability to recycle waste powder from the manufacturing process and makes for selectivity tailoring desirable properties and thus the performance of the implant Electron Beam Melting EBM and Selective Laser Melting SLM are two methods applicable for freeform fabrication of Ti alloys Manufacturing parameters greatly influence the microstructure of the product where e g a fast cooling rate in combination with low degree of melting in SLM leads to the predominant formation of martensitic alpha prime phase giving a very hard product 22 Ti 6Al 4V Ti 6Al 4V ELI This alloy has good biocompatibility and is neither cytotoxic nor genotoxic 23 Ti 6Al 4V suffers from poor shear strength and poor surface wear properties in certain loading conditions 10 Bio compatibility Excellent especially when direct contact with tissue or bone is required Ti 6Al 4V s poor shear strength makes it undesirable for bone screws or plates It also has poor surface wear properties and tends to seize when in sliding contact with itself and other metals Surface treatments such as nitriding and oxidizing can improve the surface wear properties 10 Ti 6Al 7Nb This alloy was developed as a biomedical replacement for Ti 6Al 4V because Ti 6Al 4V contains vanadium an element that has demonstrated cytotoxic outcomes when isolated 24 1 Ti 6Al 7Nb contains 6 aluminium and 7 niobium 24 18 Ti6Al7Nb is a dedicated high strength titanium alloy with excellent biocompatibility for surgical implants Used for replacement hip joints it has been in clinical use since early 1986 25 References EditNotes In a titanium or titanium alloy alpha to beta transition temperature is the temperature above which the beta phase becomes thermodynamically favorable Sources Characteristics of Alpha Alpha Beta and Beta Titanium Alloys a b c d Titanium A Technical Guide ASM International 2000 ISBN 9781615030620 Najdahmadi A Zarei Hanzaki A Farghadani E 1 February 2014 Mechanical properties enhancement in Ti 29Nb 13Ta 4 6Zr alloy via heat treatment with no detrimental effect on its biocompatibility Materials amp Design 54 786 791 doi 10 1016 j matdes 2013 09 007 ISSN 0261 3069 Goldberg Jon Burstone Charles J 1979 An Evaluation of Beta Titanium Alloys for Use in Orthodontic Appliances Journal of Dental Research 58 2 593 599 doi 10 1177 00220345790580020901 PMID 283089 S2CID 29064479 De Fontaine D Paton N E Williams J C November 1971 Transformation de la phase omega dans les alliages de titane comme exemple de reactions controlees par deplacementDie omega phasenumwandlung in titanlegierungen als beispiel einer verschiebungskontrollierten reaktion Acta Metallurgica 19 11 1153 1162 doi 10 1016 0001 6160 71 90047 2 Retrieved 27 April 2020 Ishida Taku Wakai Eiichi Makimura Shunsuke Casella Andrew M Edwards Danny J Senor David J Ammigan Kavin Hurh Patrick G Densham Christopher J Fitton Michael D Bennett Joe M Kim Dohyun Simos Nikolaos Hagiwara Masayuki Kawamura Naritoshi Meigo Shin ichiro Yohehara Katsuya 2020 Tensile behavior of dual phase titanium alloys under high intensity proton beam exposure Radiation induced omega phase transformation in Ti 6Al 4V Journal of Nuclear Materials 541 152413 arXiv 2004 11562 doi 10 1016 j jnucmat 2020 152413 S2CID 216144772 Vydehi Arun Joshi Titanium Alloys An Atlas of Structures and Fracture Features CRC Press 2006 a b c ASTM B861 10 Standard Specification for Titanium and Titanium Alloy Seamless Pipe Grades 1 to 38 Titanium Grades Application a b c d Titanium 6 4 Retrieved 2009 02 19 Compare Materials Commercially Pure Titanium and 6Al 4V Grade 5 Titanium Titanium Alloys Ti6Al4V Grade 5 Material Properties Data 6Al 4V Grade 5 Titanium Alloy Material Properties Data Marine Grade Stainless Steel Material Properties Data 6061 T6 Aluminum 6Al 4V Titanium Performance Titanium Group Titanium Ti 5Al 2 5Sn Grade 6 Material Web a b Titanium Grade 7 Titanium Palladium alloy Ti IIPd Metals Alloys and Sputtering Targets Archived from the original on 2012 04 26 Retrieved 2011 12 19 a b c d Titanium Grade Overview a b 6Al 4V ELI Titanium Performance Titanium Group ArmyCorrosion com dead link a b Murr L E Quinones S A Gaytan S M Lopez M I Rodela A Martinez E Y Hernandez D H Martinez E Medina F 2009 01 01 Microstructure and mechanical behavior of Ti 6Al 4V produced by rapid layer manufacturing for biomedical applications Journal of the Mechanical Behavior of Biomedical Materials 2 1 20 32 doi 10 1016 j jmbbm 2008 05 004 PMID 19627804 Velasco Ortega E Sep 2010 In vitro evaluation of cytotoxicity and genotoxicity of a commercial titanium alloy for dental implantology Mutat Res 702 1 17 23 doi 10 1016 j mrgentox 2010 06 013 PMID 20615479 a b The fatigue resistance of commercially pure titanium grade II titanium alloy Ti6Al7Nb and conventional cobalt chromium cast clasps by Mali Palanuwech Inaugural Dissertation zur Erlangung des Doktorgrades der Zahnheilkunde der Medizinschen Fakultat der Eberhard Karls Universitat zu Tubingenvorgelegt Munich 2003 Retrieved 8 September 2012 Titanium Alloys Ti6Al7Nb Properties and Applications Retrieved 8 September 2012External links Edit Wikimedia Commons has media related to Titanium based alloys http www tifab com subpages tech spec grades htm Datasheet for Beta Titanium Titanium Alloy Bar Phase Stability and Stress Induced Transformations in Beta Titanium Alloys Retrieved from https en wikipedia org w index php title Titanium alloys amp oldid 1138632236, wikipedia, wiki, book, books, library,

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