Titanium aluminide
Encyclopedia
Titanium aluminide, Ti
Al
, is an intermetallic
chemical compound
. It is lightweight and resistant to oxidation and heat, however it suffers from low ductility
. The density of gamma TiAl is about 4.0 g/cm³. It finds use in several applications including automobiles and aircraft. The development of TiAl based alloys began about 1970; however the alloys have only been used in these applications since about 2000.
Titanium aluminide has three major intermetallic compounds: gamma TiAl, alpha 2-Ti3Al and TiAl3. Among the three, gamma TiAl has received the most interest and applications. Gamma TiAl has excellent mechanical properties and oxidation and corrosion resistance at elevated temperatures (over 600 degrees Celsius), which makes it a possible replacement for traditional Ni based superalloy
components in aircraft turbine
engines.
TiAl based alloys have a strong potential to increase the thrust-to-weight ratio in the aircraft engine. This is especially the case with the engine's low pressure turbine blades and the high pressure compressor blades. These are traditionally made up of Ni based superalloy, which is nearly twice as dense as TiAl based alloys.
General Electric
has recently announced that gamma TiAl low pressure turbine blades will be used on its GEnx
engine, which powers the Boeing 787
and Boeing 747-8
aircraft. This is the first large-scale use of this material on a commercial jet engine. The TiAl LPT blades are cast by Precision Castparts Corp.
and Avio s.p.a.
Titanium
Titanium is a chemical element with the symbol Ti and atomic number 22. It has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver color....
Al
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
, is an intermetallic
Intermetallics
Intermetallics or intermetallic compounds is a term that is used in a number of different ways. Most commonly it refers to solid-state phases involving metals. There is a "research definition" adhered to generally in scientific publications, and a wider "common use" term...
chemical compound
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
. It is lightweight and resistant to oxidation and heat, however it suffers from low ductility
Ductility
In materials science, ductility is a solid material's ability to deform under tensile stress; this is often characterized by the material's ability to be stretched into a wire. Malleability, a similar property, is a material's ability to deform under compressive stress; this is often characterized...
. The density of gamma TiAl is about 4.0 g/cm³. It finds use in several applications including automobiles and aircraft. The development of TiAl based alloys began about 1970; however the alloys have only been used in these applications since about 2000.
Titanium aluminide has three major intermetallic compounds: gamma TiAl, alpha 2-Ti3Al and TiAl3. Among the three, gamma TiAl has received the most interest and applications. Gamma TiAl has excellent mechanical properties and oxidation and corrosion resistance at elevated temperatures (over 600 degrees Celsius), which makes it a possible replacement for traditional Ni based superalloy
Superalloy
A superalloy, or high-performance alloy, is an alloy that exhibits excellent mechanical strength and creep resistance at high temperatures, good surface stability, and corrosion and oxidation resistance. Superalloys typically have a matrix with an austenitic face-centered cubic crystal structure. ...
components in aircraft turbine
Turbine
A turbine is a rotary engine that extracts energy from a fluid flow and converts it into useful work.The simplest turbines have one moving part, a rotor assembly, which is a shaft or drum with blades attached. Moving fluid acts on the blades, or the blades react to the flow, so that they move and...
engines.
TiAl based alloys have a strong potential to increase the thrust-to-weight ratio in the aircraft engine. This is especially the case with the engine's low pressure turbine blades and the high pressure compressor blades. These are traditionally made up of Ni based superalloy, which is nearly twice as dense as TiAl based alloys.
General Electric
General Electric
General Electric Company , or GE, is an American multinational conglomerate corporation incorporated in Schenectady, New York and headquartered in Fairfield, Connecticut, United States...
has recently announced that gamma TiAl low pressure turbine blades will be used on its GEnx
General Electric GEnx
The General Electric GEnx is an advanced dual rotor, axial flow, high-bypass turbofan jet engine in production by GE Aviation for the Boeing 787 and 747-8...
engine, which powers the Boeing 787
Boeing 787
The Boeing 787 Dreamliner is a long-range, mid-size wide-body, twin-engine jet airliner developed by Boeing Commercial Airplanes. It seats 210 to 290 passengers, depending on the variant. Boeing states that it is the company's most fuel-efficient airliner and the world's first major airliner to use...
and Boeing 747-8
Boeing 747-8
The Boeing 747-8 is a wide-body jet airliner developed by Boeing Commercial Airplanes. Officially announced in 2005, the 747-8 is the fourth-generation Boeing 747 version, with lengthened fuselage, redesigned wings and improved efficiency...
aircraft. This is the first large-scale use of this material on a commercial jet engine. The TiAl LPT blades are cast by Precision Castparts Corp.
Precision Castparts Corp.
Precision Castparts Corp. is a Portland, Oregon, United States-based industrial goods and metal fabrication company that manufactures cast metal parts for use in the aerospace, industrial, defense, and automobile industries. In 2009 they ranked 362nd on the Fortune 500 list, and 11th in the...
and Avio s.p.a.