Titanium alloys are
alloy
An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductility, ...
s that contain a mixture of
titanium
Titanium is a chemical element with the symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resistant to corrosion in ...
and other
chemical element
A chemical element is a species of atoms that have a given number of protons in their nuclei, including the pure substance consisting only of that species. Unlike chemical compounds, chemical elements cannot be broken down into simpler sub ...
s. Such alloys have very high
tensile strength
Ultimate tensile strength (UTS), often shortened to tensile strength (TS), ultimate strength, or F_\text within equations, is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle materials t ...
and
toughness
In materials science and metallurgy, toughness is the ability of a material to absorb energy and plastically deform without fracturing.[corrosion resistance
Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engine ...]
and the ability to withstand extreme temperatures. However, the high cost of both raw materials and processing limit their use to
military
A military, also known collectively as armed forces, is a heavily armed, highly organized force primarily intended for warfare. It is typically authorized and maintained by a sovereign state, with its members identifiable by their distinct ...
applications,
aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines ...
,
spacecraft
A spacecraft is a vehicle or machine designed to fly in outer space. A type of artificial satellite, spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, p ...
,
bicycle
A bicycle, also called a pedal cycle, bike or cycle, is a human-powered or motor-powered assisted, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A is called a cyclist, or bicyclist.
Bic ...
s, medical devices, jewelry, highly stressed components such as
connecting rod
A connecting rod, also called a 'con rod', is the part of a piston engine which connects the piston to the crankshaft. Together with the crank, the connecting rod converts the reciprocating motion of the piston into the rotation of the cranksh ...
s on expensive
sports car
A sports car is a car designed with an emphasis on dynamic performance, such as handling, acceleration, top speed, the thrill of driving and racing capability. Sports cars originated in Europe in the early 1900s and are currently produced by ...
s and some premium
sports equipment
Sports equipment, sporting equipment, also called sporting goods, are the tools, materials, apparel, and gear used to compete in a sport and varies depending on the sport. The equipment ranges from balls, nets, and protective gear like helmets. ...
and
consumer electronics
Consumer electronics or home electronics are electronic (analog or digital) equipment intended for everyday use, typically in private homes. Consumer electronics include devices used for entertainment, communications and recreation. Usually r ...
.
Although "commercially pure" titanium has acceptable mechanical properties and has been used for
orthopedic
Orthopedic surgery or orthopedics ( alternatively spelt orthopaedics), is the branch of surgery concerned with conditions involving the musculoskeletal system. Orthopedic surgeons use both surgical and nonsurgical means to treat musculoskeletal ...
and
dental implants
A dental implant (also known as an endosseous implant or fixture) is a prosthesis that interfaces with the bone of the jaw or skull to support a dental prosthesis such as a crown, bridge, denture, or facial prosthesis or to act as an orthodonti ...
, for most applications titanium is alloyed with small amounts of
aluminium
Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...
and
vanadium
Vanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery-grey, malleable transition metal. The elemental metal is rarely found in nature, but once isolated artificially, the formation of an oxide layer ( pas ...
, typically 6% and 4% respectively, by weight. This mixture has a
solid solubility
In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution.
The extent of the solub ...
which varies dramatically with temperature, allowing it to undergo
precipitation strengthening
Precipitation hardening, also called age hardening or particle hardening, is a heat treatment technique used to increase the yield strength of malleable materials, including most structural alloys of aluminium, magnesium, nickel, titanium, and so ...
. This
heat treatment
Heat treating (or heat treatment) is a group of industrial, thermal and metalworking processes used to alter the physical, and sometimes chemical, properties of a material. The most common application is metallurgical. Heat treatments are also ...
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:
* Alpha alloys which contain neutral alloying elements (such as
tin
Tin is a chemical element with the symbol Sn (from la, stannum) and atomic number 50. Tin is a silvery-coloured metal.
Tin is soft enough to be cut with little force and a bar of tin can be bent by hand with little effort. When bent, t ...
) and/ or alpha stabilisers (such as aluminium or
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
) only. These are not heat treatable. Examples include:
Ti-5Al-2Sn-ELI, Ti-8Al-1Mo-1V.
* Near-alpha alloys contain small amount of
ductile
Ductility is a mechanical property commonly described as a material's amenability to drawing (e.g. into wire). In materials science, ductility is defined by the degree to which a material can sustain plastic deformation under tensile stres ...
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:
Ti-6Al-2Sn-4Zr-2Mo Ti-6Al-2Sn-4Zr-2Mo (UNS designation R54620), also known as Ti 6-2-4-2, is a near alpha titanium alloy known for its high strength and excellent corrosion resistance. It is often used in the aerospace industry for creating high-temperature jet engin ...
, 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:
Ti-6Al-4V Ti-6Al-4V (UNS designation R56400), also sometimes called TC4, Ti64, or ASTM Grade 5, is an alpha-beta titanium alloy with a high specific strength and excellent corrosion resistance. It is one of the most commonly used titanium alloys and is applie ...
, Ti-6Al-4V-ELI, Ti-6Al-6V-2Sn,
Ti-6Al-7Nb Ti-6Al-7Nb (UNS designation R56700) is an alpha-beta titanium alloy first synthesized in 1977 containing 6% aluminum and 7% niobium. It features high strength and has similar properties as the cytotoxic vanadium containing alloy Ti-6Al-4V. Ti-6Al-7N ...
.
* 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:
Ti-10V-2Fe-3Al Ti-10V-2Fe-3Al (UNS designation R56410), also known as Ti 10-2-3, is a non-ferrous near-beta titanium alloy featuring an excellent combination of strength, ductility, fracture toughness and high cycle fatigue strength. It is typically used in the ae ...
, Ti–29Nb–13Ta–4.6Zr, Ti-13V-11Cr-3Al, Ti-8Mo-8V-2Fe-3Al, Beta C, Ti-15-3.
Beta-titanium
Beta titanium
alloy
An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductility, ...
s exhibit the
BCC allotropic
Allotropy or allotropism () is the property of some chemical elements to exist in two or more different forms, in the same physical state, known as allotropes of the elements. Allotropes are different structural modifications of an element: th ...
form of
titanium
Titanium is a chemical element with the symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resistant to corrosion in ...
(called beta). Elements used in this alloy are one or more of the following other than titanium in varying amounts. These are
molybdenum
Molybdenum is a chemical element with the symbol Mo and atomic number 42 which is located in period 5 and group 6. The name is from Neo-Latin ''molybdaenum'', which is based on Ancient Greek ', meaning lead, since its ores were confused with lea ...
,
vanadium
Vanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery-grey, malleable transition metal. The elemental metal is rarely found in nature, but once isolated artificially, the formation of an oxide layer ( pas ...
,
niobium
Niobium is a chemical element with chemical symbol Nb (formerly columbium, Cb) and atomic number 41. It is a light grey, crystalline, and ductile transition metal. Pure niobium has a Mohs hardness rating similar to pure titanium, and it has sim ...
,
tantalum
Tantalum is a chemical element with the symbol Ta and atomic number 73. Previously known as ''tantalium'', it is named after Tantalus, a villain in Greek mythology. Tantalum is a very hard, ductile, lustrous, blue-gray transition metal that is ...
,
zirconium
Zirconium is a chemical element with the symbol Zr and atomic number 40. The name ''zirconium'' is taken from the name of the mineral zircon, the most important source of zirconium. The word is related to Persian '' zargun'' (zircon; ''zar-gun'', ...
,
manganese
Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy use ...
,
iron
Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...
,
chromium
Chromium is a chemical element with the symbol Cr and atomic number 24. It is the first element in group 6. It is a steely-grey, lustrous, hard, and brittle transition metal.
Chromium metal is valued for its high corrosion resistance and hardne ...
,
cobalt
Cobalt is a chemical element with the symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, pr ...
,
nickel
Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow to ...
, and
copper
Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...
.
The titanium alloys have excellent formability and can be easily welded.
Beta titanium is nowadays largely utilized in the
orthodontic
Orthodontics is a dentistry specialty that addresses the diagnosis, prevention, management, and correction of mal-positioned teeth and jaws, and misaligned bite patterns. It may also address the modification of facial growth, known as dentofacial ...
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
alloy
An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductility, ...
s can convert to hard and brittle
hexagonal
In geometry, a hexagon (from Greek , , meaning "six", and , , meaning "corner, angle") is a six-sided polygon. The total of the internal angles of any simple (non-self-intersecting) hexagon is 720°.
Regular hexagon
A '' regular hexagon'' has ...
omega-titanium at cryogenic temperatures or under influence of ionizing radiation.
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
Allotropy or allotropism () is the property of some chemical elements to exist in two or more different forms, in the same physical state, known as allotropes of the elements. Allotropes are different structural modifications of an element: th ...
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
Transition temperature is the temperature at which a material changes from one crystal state (allotrope) to another. More formally, it is the temperature at which two crystalline forms of a substance can co-exist in equilibrium. For example, when ...
, while others (beta stabilizers) lower the transition temperature. Aluminium,
gallium
Gallium is a chemical element with the symbol Ga and atomic number 31. Discovered by French chemist Paul-Émile Lecoq de Boisbaudran in 1875, Gallium is in group 13 of the periodic table and is similar to the other metals of the group (aluminiu ...
,
germanium
Germanium is a chemical element with the symbol Ge and atomic number 32. It is lustrous, hard-brittle, grayish-white and similar in appearance to silicon. It is a metalloid in the carbon group that is chemically similar to its group neighbors s ...
,
carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent
In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...
,
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
and
nitrogen
Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
are alpha stabilizers.
Molybdenum
Molybdenum is a chemical element with the symbol Mo and atomic number 42 which is located in period 5 and group 6. The name is from Neo-Latin ''molybdaenum'', which is based on Ancient Greek ', meaning lead, since its ores were confused with lea ...
,
vanadium
Vanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery-grey, malleable transition metal. The elemental metal is rarely found in nature, but once isolated artificially, the formation of an oxide layer ( pas ...
,
tantalum
Tantalum is a chemical element with the symbol Ta and atomic number 73. Previously known as ''tantalium'', it is named after Tantalus, a villain in Greek mythology. Tantalum is a very hard, ductile, lustrous, blue-gray transition metal that is ...
,
niobium
Niobium is a chemical element with chemical symbol Nb (formerly columbium, Cb) and atomic number 41. It is a light grey, crystalline, and ductile transition metal. Pure niobium has a Mohs hardness rating similar to pure titanium, and it has sim ...
,
manganese
Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy use ...
,
iron
Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...
,
chromium
Chromium is a chemical element with the symbol Cr and atomic number 24. It is the first element in group 6. It is a steely-grey, lustrous, hard, and brittle transition metal.
Chromium metal is valued for its high corrosion resistance and hardne ...
,
cobalt
Cobalt is a chemical element with the symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, pr ...
,
nickel
Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow to ...
,
copper
Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...
and
silicon
Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic tab ...
are beta stabilizers.
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
Titanium dioxide, also known as titanium(IV) oxide or titania , is the inorganic compound with the chemical formula . When used as a pigment, it is called titanium white, Pigment White 6 (PW6), or CI 77891. It is a white solid that is insolubl ...
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
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
, 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
ASTM International, formerly known as American Society for Testing and Materials, is an international standards organization that develops and publishes voluntary consensus technical standards for a wide range of materials, products, systems, an ...
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."[ASTM B861 – 10 Standard Specification for Titanium and Titanium Alloy Seamless Pipe (Grades 1 to 38)]
/ref>
"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."
"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."
; 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.
; 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 Ti-6Al-4V (UNS designation R56400), also sometimes called TC4, Ti64, or ASTM Grade 5, is an alpha-beta titanium alloy with a high specific strength and excellent corrosion resistance. It is one of the most commonly used titanium alloys and is applie ...
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
Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...
, 0.2% (maximum)
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
, and the remainder titanium.
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). 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."[Titanium Alloys – Ti6Al4V Grade 5](_blank)
/ref>
"''Applications'': Blades, discs, rings, airframes, fasteners, components. Vessels, cases, hubs, forgings. Biomedical implants."
:Generally, Ti-6Al-4V is used in applications up to 400 degrees Celsius. It has a
density
Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematical ...
of roughly 4420 kg/m
3,
Young's modulus
Young's modulus E, the Young modulus, or the modulus of elasticity in tension or compression (i.e., negative tension), is a mechanical property that measures the tensile or compressive stiffness of a solid material when the force is applied leng ...
of 120 GPa, and
tensile strength
Ultimate tensile strength (UTS), often shortened to tensile strength (TS), ultimate strength, or F_\text within equations, is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle materials t ...
of 1000 MPa. By comparison, annealed type 316 stainless steel has a density of 8000 kg/m
3, modulus of 193 GPa, and tensile strength of 570 MPa. Tempered
6061 aluminium alloy
6061 ( Unified Numbering System (UNS) designation A96061) is a precipitation-hardened aluminium alloy, containing magnesium and silicon as its major alloying elements. Originally called "Alloy 61S", it was developed in 1935. It has good mechani ...
has a density of 2700 kg/m
3, modulus of 69 GPa, and tensile strength of 310 MPa, respectively.
:Ti-6Al-4V standard specifications include:
::* 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.
; Grade 7: contains 0.12 to 0.25%
palladium
Palladium is a chemical element with the symbol Pd and atomic number 46. It is a rare and lustrous silvery-white metal discovered in 1803 by the English chemist William Hyde Wollaston. He named it after the asteroid Pallas, which was itself na ...
. 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.
; Grade 7H: is identical to Grade 7 with enhanced corrosion resistance.
; 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.
[Titanium Grade Overview](_blank)
/ref>
; Grade 12: contains 0.3% molybdenum and 0.8% nickel.
; Grades 13, 14, and 15: all contain 0.5% nickel and 0.05% ruthenium
Ruthenium is a chemical element with the Symbol (chemistry), symbol Ru and atomic number 44. It is a rare transition metal belonging to the platinum group of the periodic table. Like the other metals of the platinum group, ruthenium is inert to ...
.
; 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.
; 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.
; 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
Niobium is a chemical element with chemical symbol Nb (formerly columbium, Cb) and atomic number 41. It is a light grey, crystalline, and ductile transition metal. Pure niobium has a Mohs hardness rating similar to pure titanium, and it has sim ...
, 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
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
and iron
Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...
improve ductility and fracture toughness with some reduction in strength. TAV-ELI is the most commonly used medical implant-grade titanium alloy.
:Ti-6Al-4V-ELI standard specifications include:
::* 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 .
; 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.
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 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
Numerical control (also computer numerical control, and commonly called CNC) is the automated control of machining tools (such as drills, lathes, mills, grinders, routers and 3D printers) by means of a computer. A CNC machine processes a p ...
, CAD
Computer-aided design (CAD) is the use of computers (or ) to aid in the creation, modification, analysis, or optimization of a design. This software is used to increase the productivity of the designer, improve the quality of design, improve co ...
-driven machining, or powder metallurgy
Powder metallurgy (PM) is a term covering a wide range of ways in which materials or components are made from metal powders. PM processes can reduce or eliminate the need for subtractive processes in manufacturing, lowering material losses and ...
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
Precipitation hardening, also called age hardening or particle hardening, is a heat treatment technique used to increase the yield strength of malleable materials, including most structural alloys of aluminium, magnesium, nickel, titanium, and so ...
), 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.
With the emergence of solid freeform fabrication (3D printing
3D printing or additive manufacturing is the Manufacturing, construction of a three-dimensional object from a computer-aided design, CAD model or a digital 3D modeling, 3D model. It can be done in a variety of processes in which material is ...
) 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
Electron-beam additive manufacturing, or electron-beam melting (EBM) is a type of additive manufacturing, or 3D printing, for metal parts. The raw material (metal powder or wire) is placed under a vacuum and fused together from heating by an ele ...
(EBM) and Selective Laser Melting
Selective laser melting (SLM) is one of many proprietary names for a metal additive manufacturing (AM) technology that uses a bed of powder with a source of heat to create metal parts. Also known as direct metal laser sintering (DMLS), the ASTM ...
(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.
; Ti-6Al-4V Ti-6Al-4V (UNS designation R56400), also sometimes called TC4, Ti64, or ASTM Grade 5, is an alpha-beta titanium alloy with a high specific strength and excellent corrosion resistance. It is one of the most commonly used titanium alloys and is applie ...
/ Ti-6Al-4V-ELI: This alloy has good biocompatibility, and is neither cytotoxic nor genotoxic. Ti-6Al-4V suffers from poor shear strength and poor surface wear properties in certain loading conditions:''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.
; Ti-6Al-7Nb Ti-6Al-7Nb (UNS designation R56700) is an alpha-beta titanium alloy first synthesized in 1977 containing 6% aluminum and 7% niobium. It features high strength and has similar properties as the cytotoxic vanadium containing alloy Ti-6Al-4V. Ti-6Al-7N ...
: 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.[''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](_blank)
/ref> Ti-6Al-7Nb contains 6% aluminium and 7% niobium.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.[Titanium Alloys – Ti6Al7Nb Properties and Applications. Retrieved 8 September 2012](_blank)
/ref>
References
;Notes
;Sources
External links
* 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
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