Titanium aluminide

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Contents

Titanium aluminide
Names
IUPAC name
aluminum;titanium
Identifiers
3D model (JSmol)
ChemSpider
PubChem CID
  • InChI=1S/Al.Ti
    Key: KHEQKSIHRDRLMG-UHFFFAOYSA-N
  • [Al].[Ti]
Properties
AlTi
Molar mass 74.849 g/mol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Titanium aluminide (chemical formula TiAl), commonly gamma titanium, is an intermetallic chemical compound. It is lightweight and resistant to oxidation [1] and heat, but has low ductility. The density of γ-TiAl is about 4.0 g/cm3. It finds use in several applications including aircraft, jet engines, sporting equipment and automobiles.[ citation needed ] The development of TiAl based alloys began circa 1970. The alloys have been used in these applications only since about 2000.

Titanium aluminide has three major intermetallic compounds: gamma titanium aluminide (gamma TiAl, γ-TiAl), alpha 2-Ti3Al and TiAl3. Among the three, gamma TiAl has received the most interest and applications.

Applications of gamma-TiAl

Pole figures displaying crystallographic texture of gamma-TiAl in a rolled sheet of alpha2-gamma alloy, as measured by high energy X-rays. MAUD-MTEX-TiAl-hasylab-2003-Liss.png
Pole figures displaying crystallographic texture of gamma-TiAl in a rolled sheet of alpha2-gamma alloy, as measured by high energy X-rays.

Gamma TiAl has excellent mechanical properties and oxidation and corrosion resistance at elevated temperatures (over 600 °C), which makes it a possible replacement for traditional Ni based superalloy components in aircraft turbine engines.

TiAl-based alloys have potential to increase the thrust-to-weight ratio in aircraft engines. This is especially the case with the engine's low-pressure turbine blades and the high-pressure compressor blades. These are traditionally made of Ni-based superalloy, which is nearly twice as dense as TiAl-based alloys. Some gamma titanium aluminide alloys retain strength and oxidation resistance to 1000 °C, which is 400 °C higher than the operating temperature limit of conventional titanium alloys.[ not specific enough to verify ] [3]

General Electric uses gamma TiAl for the low-pressure turbine blades on its GEnx engine, which powers the Boeing 787 and Boeing 747-8 aircraft. This was the first large-scale use of this material on a commercial jet engine [4] when it entered service in 2011. [5] The TiAl LPT blades are cast by Precision Castparts Corp. and Avio s.p.a. Machining of the Stage 6, and Stage 7 LPT blades is performed by Moeller Manufacturing. [6] [ citation needed ] An alternate pathway for production of the gamma TiAl blades for the GEnx and GE9x engines using additive manufacturing is being explored. [7]

In 2019 a new 55 g lightweight version of the Omega Seamaster wristwatch was made, using gamma titanium aluminide for the case, backcase and crown, and a titanium dial and mechanism in Ti 6/4 (grade 5). The retail price of this watch at £37,240 was nine times that of the basic Seamaster and comparable to the top of the range platinum-cased version with a moonphase complication. [8]

Alpha 2-Ti3Al

TiAl3

TiAl3 has the lowest density of 3.4 g/cm3, the highest micro hardness of 465–670 kg/mm2 and the best oxidation resistance even at 1 000 °C. However, the applications of TiAl3 in the engineering and aerospace fields are limited by its poor ductility. In addition, the loss of ductility at ambient temperature is usually accompanied by a change of fracture mode from ductile transgranular to brittle intergranular or to brittle cleavage. Despite the fact that a lot of toughening strategies have been developed to improve their toughness, machining quality is still a difficult problem to tackle. Near-net shape manufacturing technology is considered as one of the best choices for preparing such materials. {date=July 2022}[ citation needed ]

Related Research Articles

<span class="mw-page-title-main">Metal</span> Type of material

A metal is a material that, when polished or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. These properties are all associated with having electrons available at the Fermi level, as against nonmetallic materials which do not. Metals are typically ductile and malleable.

<span class="mw-page-title-main">Titanium</span> Chemical element with atomic number 22 (Ti)

Titanium is a chemical element; it has 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 sea water, aqua regia, and chlorine.

<span class="mw-page-title-main">Creep (deformation)</span> Tendency of a solid material to move slowly or deform permanently under mechanical stress

In materials science, creep is the tendency of a solid material to undergo slow deformation while subject to persistent mechanical stresses. It can occur as a result of long-term exposure to high levels of stress that are still below the yield strength of the material. Creep is more severe in materials that are subjected to heat for long periods and generally increases as they near their melting point.

A cermet is a composite material composed of ceramic and metal materials.

<span class="mw-page-title-main">Intermetallic</span> Type of metallic alloy

An intermetallic is a type of metallic alloy that forms an ordered solid-state compound between two or more metallic elements. Intermetallics are generally hard and brittle, with good high-temperature mechanical properties. They can be classified as stoichiometric or nonstoichiometic.

<span class="mw-page-title-main">Inconel</span> Austenitic nickel-chromium superalloys

Inconel is a nickel-chromium-based superalloy often utilized in extreme environments where components are subjected to high temperature, pressure or mechanical loads. Inconel alloys are oxidation- and corrosion-resistant. When heated, Inconel forms a thick, stable, passivating oxide layer protecting the surface from further attack. Inconel retains strength over a wide temperature range, attractive for high-temperature applications where aluminum and steel would succumb to creep as a result of thermally-induced crystal vacancies. Inconel's high-temperature strength is developed by solid solution strengthening or precipitation hardening, depending on the alloy.

<span class="mw-page-title-main">Titanium alloys</span> Metal alloys made by combining titanium with other elements

Titanium alloys are alloys that contain a mixture of titanium and other chemical elements. Such alloys have very high tensile strength and toughness. They are light in weight, have extraordinary corrosion resistance and the ability to withstand extreme temperatures. However, the high cost of processing limits 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.

<span class="mw-page-title-main">Superalloy</span> Alloy with higher durability than normal metals

A superalloy, or high-performance alloy, is an alloy with the ability to operate at a high fraction of its melting point. Key characteristics of a superalloy include mechanical strength, thermal creep deformation resistance, surface stability, and corrosion and oxidation resistance.

<span class="mw-page-title-main">Titanium hydride</span> Chemical compound

Titanium hydride normally refers to the inorganic compound TiH2 and related nonstoichiometric materials. It is commercially available as a stable grey/black powder, which is used as an additive in the production of Alnico sintered magnets, in the sintering of powdered metals, the production of metal foam, the production of powdered titanium metal and in pyrotechnics.

Nickel aluminide refers to either of two widely used intermetallic compounds, Ni3Al or NiAl, but the term is sometimes used to refer to any nickel–aluminium alloy. These alloys are widely used because of their high strength even at high temperature, low density, corrosion resistance, and ease of production. Ni3Al is of specific interest as a precipitate in nickel-based superalloys, where it is called the γ' (gamma prime) phase. It gives these alloys high strength and creep resistance up to 0.7–0.8 of its melting temperature. Meanwhile, NiAl displays excellent properties such as lower density and higher melting temperature than those of Ni3Al, and good thermal conductivity and oxidation resistance. These properties make it attractive for special high-temperature applications like coatings on blades in gas turbines and jet engines. However, both these alloys have the disadvantage of being quite brittle at room temperature, with Ni3Al remaining brittle at high temperatures as well. To address this problem, has been shown that Ni3Al can be made ductile when manufactured in single-crystal form rather than in polycrystalline form.

Electron-beam additive manufacturing, or electron-beam melting (EBM) is a type of additive manufacturing, or 3D printing, for metal parts. The raw material is placed under a vacuum and fused together from heating by an electron beam. This technique is distinct from selective laser sintering as the raw material fuses have completely melted. Selective Electron Beam Melting (SEBM) emerged as a powder bed-based additive manufacturing (AM) technology and was brought to market in 1997 by Arcam AB Corporation headquartered in Sweden.

<span class="mw-page-title-main">Directional solidification</span> Types of solidification within castings

Directional solidification(DS) and progressive solidification are types of solidification within castings. Directional solidification is solidification that occurs from farthest end of the casting and works its way towards the sprue. Progressive solidification, also known as parallel solidification, is solidification that starts at the walls of the casting and progresses perpendicularly from that surface.

Defence Metallurgical Research Laboratory (DMRL) is a research laboratory of the Defence Research and Development Organisation (DRDO). Located in Defence Research Complex, Kanchanbagh, Hyderabad. It is responsible for the development and manufacture of complex metals and materials required for modern warfare and weapon systems.

<span class="mw-page-title-main">Turbine blade</span> Aerofoil; individual component of a turbine disc

A turbine blade is a radial aerofoil mounted in the rim of a turbine disc and which produces a tangential force which rotates a turbine rotor. Each turbine disc has many blades. As such they are used in gas turbine engines and steam turbines. The blades are responsible for extracting energy from the high temperature, high pressure gas produced by the combustor. The turbine blades are often the limiting component of gas turbines. To survive in this difficult environment, turbine blades often use exotic materials like superalloys and many different methods of cooling that can be categorized as internal and external cooling, and thermal barrier coatings. Blade fatigue is a major source of failure in steam turbines and gas turbines. Fatigue is caused by the stress induced by vibration and resonance within the operating range of machinery. To protect blades from these high dynamic stresses, friction dampers are used.

<span class="mw-page-title-main">Waspaloy</span> Nickel-based superalloy, United Technologies Corp trademark

Waspaloy is a registered trademark of United Technologies Corp that refers to an age hardening austenitic nickel-based superalloy. Waspaloy is typically used in high temperature applications, particularly in gas turbines.

<span class="mw-page-title-main">Mechanical alloying</span>

Mechanical alloying (MA) is a solid-state and powder processing technique involving repeated cold welding, fracturing, and re-welding of blended powder particles in a high-energy ball mill to produce a homogeneous material. Originally developed to produce oxide-dispersion strengthened (ODS) nickel- and iron-base superalloys for applications in the aerospace industry, MA has now been shown to be capable of synthesizing a variety of equilibrium and non-equilibrium alloy phases starting from blended elemental or pre-alloyed powders. The non-equilibrium phases synthesized include supersaturated solid solutions, metastable crystalline and quasicrystalline phases, nanostructures, and amorphous alloys.The method is sometimes is classified as a surface severe platic deformation method to achieve nanomaterials.

<span class="mw-page-title-main">Mishra Dhatu Nigam</span> Metallurgy industry

Mishra Dhatu Nigam Limited is a metals and metal alloys manufacturing facility in Hyderabad, Telangana, India. It operates as a Public Sector Undertaking (PSU) under the administrative control of Department of Defence Production Ministry of Defence, Government of India. MIDHANI is the only producer of titanium in India.

A niobium alloy is one in which the most common element is niobium.

<span class="mw-page-title-main">Inconel 625</span> Nickel-based superalloy

Inconel Alloy 625 is a nickel-based superalloy that possesses high strength properties and resistance to elevated temperatures. It also demonstrates remarkable protection against corrosion and oxidation. Its ability to withstand high stress and a wide range of temperatures, both in and out of water, as well as being able to resist corrosion while being exposed to highly acidic environments makes it a fitting choice for nuclear and marine applications.

Iron aluminides are intermetallic compounds of iron and aluminium - they typically contain ~18% Al or more.

References

  1. ↑ Voskoboinikov R, Lumpkin G, Middleburgh S (2013). "Preferential formation of Al self-interstitial defects in γ-TiAl under irradiation". Intermetallics . 32: 230–232. doi:10.1016/j.intermet.2012.07.026.
  2. ↑ Liss KD, Bartels A, Schreyer A, Clemens H (2003). "High energy X-rays: A tool for advanced bulk investigations in materials science and physics". Textures Microstruct. 35 (3/4): 219–52. doi: 10.1080/07303300310001634952 .
  3. ↑ Thomas M, Bacos MP (November 2011). "Processing and Characterization of TiAl-based Alloys : Towards an Industrial Scale". Aerospace Lab. 3: 1–11.
  4. ↑ Bewlay BP, Nag S, Suzuki A, Weimer MJ (2016). "TiAl alloys in commercial aircraft engines". Materials at High Temperatures . 33 (4–5): 549–559. Bibcode:2016MaHT...33..549B. doi:10.1080/09603409.2016.1183068. S2CID   138071925.
  5. ↑ "GE Aviation Rolls Out its 1,000th GEnx Engine". AviationPros. 21 October 2015. Retrieved 10 August 2017.
  6. ↑ Moeller Manufacturing, Aerospace Division, in Wixom, Michigan, USA
  7. ↑ Heidi Milkert (18 August 2014). "GE Uses Breakthrough New Electron Gun For 3D Printing – 10X's More Powerful Than Laser Sintering". 3D Print.com.
  8. ↑ Tim Barber (31 August 2019). "The new Omega Seamaster Aqua Terra is made of titanium and weighs just 55g". Wired .
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