Titanium aluminide
Names
IUPAC name
aluminum;titanium
Identifiers
3D model (JSmol)
ChemSpider
  • 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.[2]

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]

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.

External links

source: http://en.wikipedia.org/wiki/Titanium_aluminide