Titanium aluminide

[[File:MAUD-MTEX-TiAl-hasylab-2003-Liss.png|thumb|Pole figures displaying crystallographic texture of gamma-TiAl in a rolled sheet of alpha2-gamma alloy, as measured by high energy X-rays.{{cite journal

|vauthors=Liss KD, Bartels A, Schreyer A, Clemens H

|title=High energy X-rays: A tool for advanced bulk investigations in materials science and physics

|journal=Textures Microstruct.

|year=2003 |volume=35 |issue=3/4 |pages=219–52

|doi=10.1080/07303300310001634952

|doi-access=free

}}]]

Gamma TiAl has excellent mechanical properties and oxidation and corrosion resistance at elevated temperatures (over 600{{nbsp}}°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.{{Nonspecific|date=July 2020}}{{cite journal|title=Processing and Characterization of TiAl-based Alloys : Towards an Industrial Scale|journal=Aerospace Lab|date=November 2011|volume=3|pages=1–11|url=https://hal.archives-ouvertes.fr/hal-01183638/|last1=Thomas|first1=M.|last2=Bacos|first2=M. P.}}

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{{ cite journal

| vauthors=Bewlay BP, Nag S, Suzuki A, Weimer MJ

| title=TiAl alloys in commercial aircraft engines

| journal=Materials at High Temperatures

| year=2016 | volume=33 | issue=4–5 | pages= 549–559

| doi=10.1080/09603409.2016.1183068

| bibcode=2016MaHT...33..549B

| s2cid=138071925

}} when it entered service in 2011.{{cite web

|url= http://www.aviationpros.com/press_release/12128969/ge-aviation-rolls-out-its-1000th-genx-engine

|title= GE Aviation Rolls Out its 1,000th GEnx Engine

|date= 21 October 2015

|website= AviationPros

|access-date= 10 August 2017

}} 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.[http://www.moeller-aerospace.com/specialties/titanium-aluminide Moeller Manufacturing, Aerospace Division, in Wixom, Michigan, USA]{{citation needed|date=November 2012}} An alternate pathway for production of the gamma TiAl blades for the GEnx and GE9x engines using additive manufacturing is being explored.{{Cite web

|title=GE Uses Breakthrough New Electron Gun For 3D Printing – 10X's More Powerful Than Laser Sintering

|website=3D Print.com

|date=18 August 2014

|author=Heidi Milkert

|url=http://3dprint.com/12262/ge-ebm-3d-printing/

}}

In 2019 a new 55{{nbsp}}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.{{Cite magazine

|magazine=Wired

|date=31 August 2019

|author=Tim Barber

|title=The new Omega Seamaster Aqua Terra is made of titanium and weighs just 55g

|url=https://www.wired.co.uk/article/omega-seamaster-aqua-terra-lightest-titanium

}}

Alpha 2-Ti₃Al is an intermetallic compound of titanium and aluminum, belonging to the Ti-Al system of advanced high-temperature materials. It is primarily used in aerospace and other high-performance applications due to its balance of strength, lightweight properties, and oxidation resistance.

It has an ordered hexagonal (D0₁₉) crystal structure, which makes it distinct from the more commonly known γ-TiAl (gamma titanium aluminide).

Higher strength than conventional titanium alloys, especially at high temperatures. More brittle than pure titanium but tougher than γ-TiAl, making it useful in applications requiring a trade-off between toughness and lightweight properties.

Improved high-temperature oxidation resistance compared to pure titanium, but generally not as good as γ-TiAl or other high-temperature alloys like nickel-based superalloys. Often used with coatings to further enhance oxidation resistance.

Density and Lightweight Properties:

Lower density than traditional nickel-based superalloys, making it attractive for aerospace applications where weight reduction is crucial.

Operates effectively at 600–800 °C, making it useful in jet engines, turbine components, and hypersonic vehicles.

Applications of Alpha 2-Ti₃Al:

Aerospace: Used in jet engine components, compressor blades, and airframe structures where high strength and lightweight properties are needed.

Automotive (High-Performance Vehicles): Some high-end applications in racing engines.

Military and Defense: Structural components in hypersonic aircraft and advanced missiles.

Energy Sector: Potential use in turbine components for power generation.

Challenges and Limitations:

Brittleness: More brittle than conventional titanium alloys, requiring careful processing and potential use of composite materials.

Manufacturing Complexity: Difficult to process and fabricate due to its intermetallic nature, often requiring advanced techniques like powder metallurgy, additive manufacturing, or specialized forging methods.

Oxidation Resistance: While better than standard titanium, it still requires protective coatings for long-term use in extreme environments.

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}{{cn|date=November 2022}}

{{Reflist}}

• [http://www.moeller-aerospace.com/specialties/titanium-aluminide Machining Gamma Titanium Aluminide Components - Moeller Manufacturing]
• [https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19990047462_1999064367.pdf Titanium Aluminide Applications in the HighSpeed Civil Transport]
• [http://www.azom.com/details.asp?ArticleID=1548 Titanium Aluminides - Intermetallics] on azom.com.
• [https://www.flightglobal.com/news/articles/power-house-207148/ Power House (GEnx TiAl LPT Blade Announcement)]
• {{cite journal | journal = Intermetallics | volume = 9 | issue = 12 | pages = 997–1001 | doi = 10.1016/S0966-9795(01)00064-4 | year = 2001 | title = Quo vadis gamma titanium aluminide | author = Edward A. Loria}}
• {{cite book | url=https://books.google.com/books?id=HgzukknbNGAC&pg=PA131 | page = 131 | title=Titanium: a technical guide | isbn=978-0-87170-686-7 | author1=Donachie, Matthew J | year=2000| publisher = ASM International }}
• {{cite book | url=https://books.google.com/books?id=bNfidkEOe-MC&pg=PA175| page = 175 | title=Fundamentals of creep in metals and alloys | isbn=978-0-08-043637-1 | author1=Kassner, Michael E | author2=Pérez-Prado, María-Teresa | year=2004 | publisher = Elsevier }}

{{titanium compounds}}

Category:Aluminides

Category:Titanium alloys

Category:Intermetallics