Editing Intermetallic

{{Short description|Type of metallic alloy}}
[[File:Cr11Ge19 crystals.jpg|thumb|right|255px|{{center| Cr<sub>11</sub>Ge<sub>19</sub> }}]]

An '''intermetallic''' (also called '''intermetallic compound''', '''intermetallic alloy''', '''ordered intermetallic alloy''', '''long-range-ordered alloy''') is a type of [[metallic bonding|metallic]] [[alloy]] that forms an ordered solid-state [[Chemical compound|compound]] between two or more metallic elements. Intermetallics are generally hard and brittle, with good high-temperature mechanical properties.<ref name=":0">{{Cite book|last1=Askeland|first1=Donald R.|last2=Wright|first2=Wendelin J.|url=https://www.worldcat.org/oclc/903959750|title=The science and engineering of materials|isbn=978-1-305-07676-1|edition=Seventh|location=Boston, MA|pages=387–389|chapter=11-2 Intermetallic Compounds|date=January 2015|oclc=903959750}}</ref><ref>{{Cite book|last=Panel On Intermetallic Alloy Development, Commission On Engineering And Technical Systems|url=https://www.worldcat.org/oclc/906692179|title=Intermetallic alloy development : a program evaluation|date=1997|publisher=National Academies Press|isbn=0-309-52438-5|pages=10|oclc=906692179}}</ref><ref>{{Cite book|last=Soboyejo|first= W. O.|url=http://worldcat.org/oclc/300921090|title=Mechanical properties of engineered materials|date=2003|publisher=Marcel Dekker|isbn=0-8247-8900-8|chapter=1.4.3 Intermetallics|oclc=300921090}}</ref> They can be classified as [[Stoichiometry|stoichiometric]] or nonstoichiometic.<ref name=":0" />

The term "intermetallic compounds" applied to solid phases has long been in use. However, [[William Hume-Rothery|Hume-Rothery]] argued that it misleads, suggesting a fixed stoichiometry and a clear decomposition into [[species (chemistry)|species]].<ref>{{cite book|title=Electrons, atoms, metals and alloys|first=W.|last=Hume-Rothery|publisher=Louis Cassier Co., Ltd|location=London|orig-date=1948|year=1955|edition=revised|pages=316–317|url=https://archive.org/details/in.ernet.dli.2015.18295|via=the [[Internet Archive]]}}</ref>

==Definitions==
===Research definition===
In 1967 {{interlanguage link|Gustav Ernst Robert Schulze|de}} defined intermetallic compounds as ''solid phases containing two or more metallic elements, with optionally one or more non-metallic elements, whose crystal structure differs from that of the other constituents''.<ref>G. E. R. Schulze: Metallphysik, Akademie-Verlag, Berlin 1967</ref> This definition includes:
* Electron (or [[Hume-Rothery rules|Hume-Rothery]]) compounds
* Size packing phases. e.g. [[Laves phase]]s, [[Frank–Kasper phases]] and [[Nowotny phase]]s
* [[Zintl phase]]s

The definition of metal includes:{{cn|date=March 2025}}
* [[Post-transition metal]]s, i.e. [[aluminium]], [[gallium]], [[indium]], [[thallium]], [[tin]], [[lead]], and [[bismuth]].
* [[Metalloid]]s, e.g. [[silicon]], [[germanium]], [[arsenic]], [[antimony]] and [[tellurium]].

Homogeneous and heterogeneous [[solid solution]]s of metals, and [[interstitial compound]]s such as [[carbide]]s and [[nitride]]s are excluded under this definition. However, interstitial intermetallic compounds are included, as are alloys of intermetallic compounds with a metal.{{cn|date=March 2025}}

===Common use===
In common use, the research definition, including [[post-transition metal]]s and [[metalloid]]s, is extended to include compounds such as [[cementite]], Fe<sub>3</sub>C. These compounds, sometimes termed [[interstitial compound]]s, can be [[stoichiometric]], and share properties with the above intermetallic compounds.{{cn|date=January 2024}}

===Complexes===
The term intermetallic is used<ref>{{Cotton&Wilkinson6th}}</ref> to describe compounds involving two or more metals such as the [[cyclopentadienyl complex]] Cp<sub>6</sub>Ni<sub>2</sub>Zn<sub>4</sub>.

===B2===
A [[Strukturbericht designation#B-compounds|B2]] intermetallic compound has equal numbers of atoms of two metals such as aluminum and iron, arranged as two interpenetrating simple cubic lattices of the component metals.<ref>{{cite news|title=Wings of steel: An alloy of iron and aluminium is as good as titanium, at a tenth of the cost|url=https://www.economist.com/news/science-and-technology/21642107-alloy-iron-and-aluminium-good-titanium-tenth|access-date=February 5, 2015|newspaper=The Economist|date=February 7, 2015|quote=E02715}}</ref>

==Properties==
Intermetallic compounds are generally brittle at room temperature and have high melting points. Cleavage or intergranular fracture modes are typical of intermetallics due to limited independent [[Slip (materials science)|slip]] systems required for plastic deformation. However, some intermetallics have ductile fracture modes such as Nb–15Al–40Ti. Others can exhibit improved [[ductility]] by alloying with other elements to increase grain boundary cohesion. Alloying of other materials such as [[boron]] to improve grain boundary cohesion can improve ductility.<ref>{{Cite book|last=Soboyejo|first= W. O.|url=http://worldcat.org/oclc/300921090|title=Mechanical properties of engineered materials|date=2003|publisher=Marcel Dekker|isbn=0-8247-8900-8|chapter=12.5 Fracture of Intermetallics|oclc=300921090}}</ref> They may offer a compromise between [[ceramic]] and metallic properties when hardness and/or resistance to high temperatures is important enough to sacrifice some [[toughness]] and ease of processing. They can display desirable [[magnetism|magnetic]] and chemical properties, due to their strong internal order and mixed ([[metallic bond|metallic]] and [[covalent bond|covalent]]/[[ionic bond|ionic]]) bonding, respectively. Intermetallics have given rise to various novel materials developments.{{cn|date=March 2025}}
{| class="wikitable"
|+Physical properties of intermetallics<ref name=":0" />
!Intermetallic Compound
!Melting Temperature
(°C)
!Density
(kg/m<sup>3</sup>)
!Young's Modulus (GPa)
|-
|FeAl
|1250–1400
|5600
|263
|-
|Ti<sub>3</sub>Al
|1600
|4200
|210
|-
|MoSi<sub>2</sub>
|2020
|6310
|430
|}

== Applications ==
Examples include [[alnico]] and the [[hydrogen storage]] materials in [[nickel metal hydride]] batteries. [[Nickel aluminide|Ni<sub>3</sub>Al]], which is the hardening phase in the familiar nickel-base [[superalloy|super alloy]]s, and the various [[titanium]] aluminides have attracted interest for [[turbine blade]] applications, while the latter is also used in small quantities for [[grain refinement]] of [[titanium alloy]]s. [[Silicide]]s, intermetallics involving silicon, serve as barrier and contact layers in [[microelectronics]].<ref>{{Cite journal |date=June 1993 |title=Metallization: theory and practice for VLSI and ULSI |journal=Choice Reviews Online |volume=30 |issue=10 |pages=30–5612-30-5612 |doi=10.5860/choice.30-5612 |issn=0009-4978|first=S.P. |last=Murarka |doi-broken-date=1 February 2025 }}</ref> Others include:
* [[Magnetic material]]s e.g. [[alnico]], [[sendust]], Permendur, FeCo, [[Terfenol-D]]
* [[Superconductors]] e.g. [[A15 phases]], [[niobium-tin]]
* [[Hydrogen storage]] e.g. AB<sub>5</sub> compounds ([[nickel metal hydride batteries]])
* [[Shape memory alloy]]s e.g. Cu-Al-Ni (alloys of Cu<sub>3</sub>Al and nickel), [[Nitinol]] (NiTi)
* Coating materials e.g. NiAl
* High-temperature [[structural materials]] e.g. [[nickel aluminide]], Ni<sub>3</sub>Al
* [[Dental amalgam]]s, which are alloys of intermetallics Ag<sub>3</sub>Sn and Cu<sub>3</sub>Sn
* [[Semiconductor device|Gate contact]]/ [[barrier layer]] for [[microelectronics]] e.g. [[Titanium disilicide|TiSi<sub>2</sub>]]<ref>{{cite book
| last = Ohring | first = Milton | title = Materials Science of Thin Films | publisher = Academic Press | year = 2002 | isbn = 9780125249751 | url = {{google books|plainurl=y|id=50jZ8a3_hZgC}} }}</ref>{{rp| 692}}
* [[Laves phase]]s (AB<sub>2</sub>), e.g., MgCu<sub>2</sub>, MgZn<sub>2</sub> and MgNi<sub>2</sub>.

The unintended formation of intermetallics can cause problems. For example, [[Gold-aluminium intermetallic|intermetallics of gold and aluminium]] can be a significant cause of [[wire bonding|wire bond]] failures in [[semiconductor device]]s and other [[microelectronics]] devices. The management of intermetallics is a major issue in the reliability of [[solder]] joints between electronic components.{{cn|date=January 2024}}

==Intermetallic particles==
{{Main|Intermetallic particle}}
[[Intermetallic particle]]s often form during solidification of metallic alloys, and can be used as a [[Strengthening mechanisms of materials#Dispersion strengthening|dispersion strengthening]] mechanism.<ref name=":0" />

==History==
Examples of intermetallics through history include:
* Roman yellow [[brass]], CuZn
* Chinese high tin [[bronze]], Cu<sub>31</sub>Sn<sub>8</sub>
* [[Type metal]], SbSn
* Chinese [[Cupronickel|white copper]], CuNi <ref>{{cite web|url=http://www.chinatoday.com.cn/English/e20026/sunzi1.htm|title=The Art of War by Sun Zi: A Book for All Times|publisher=[[China Today]]|access-date=2022-11-25|archive-date=2005-03-07|archive-url=https://web.archive.org/web/20050307083704/http://www.chinatoday.com.cn/English/e20026/sunzi1.htm|url-status=dead}}</ref>

German type metal is described as breaking like glass, without bending, softer than copper, but more fusible than lead.<ref>{{Cite book |first=George |last=Long |url={{google books|plainurl=y|id=joN6G1T6ZHIC}}|title=The Penny Cyclopædia of the Society for the Diffusion of Useful Knowledge |chapter=Type-pounding|date=1843 |publisher=C. Knight |language=en}}</ref>{{rp|454}} The chemical formula does not agree with the one above; however, the properties match with an intermetallic compound or an alloy of one.{{cn|date=January 2024}}

==See also==
* [[Complex metallic alloys]]
* [[Kirkendall effect]]
* [[Maraging steel]]
* [[Metallurgy]]
* [[Solid solution]]

==References==
<references />

== Sources ==
* {{cite book |last=Sauthoff |first=Gerhard |author-link=:de:Gerhard Sauthoff |url={{google books|plainurl=y|id=p75RAAAAMAAJ}} |title=Intermetallics |publisher=Wiley-VCH |year=1995 |isbn=978-3527293209 |pages=1–165}}
* {{cite book |last=Sauthoff |first=Gerhard |author-link=:de:Gerhard Sauthoff |chapter=Intermetallics |title=Ullmann's Encyclopedia of Industrial Chemistry |date=2006 |publisher=Wiley Interscience |doi=10.1002/14356007.e14_e01.pub2 |pages=393–423|isbn=978-3-527-30385-4 }}

==External links==
* [http://www.elsevier.com/wps/find/journaldescription.cws_home/423924/description#description ''Intermetallics''], scientific journal
* {{cite web|url=http://nepp.nasa.gov/wirebond/intermetallic_creation_and_growt.htm|archive-url=https://web.archive.org/web/20051218202657/http://nepp.nasa.gov/wirebond/intermetallic_creation_and_growt.htm |archive-date=December 18, 2005 |title=Intermetallic Creation and Growth}}
* {{Cite web |title=IMPRESS Intermetallics project |url=http://www.spaceflight.esa.int/impress#IMPRESS |access-date=2024-12-22 |website=www.spaceflight.esa.int
|archive-url=https://web.archive.org/web/20070329034903/http://www.spaceflight.esa.int/impress/#IMPRESS |archive-date=2007-03-29 }}
* {{cite AV media|url=https://www.ameslab.gov/mpc/video |archive-url=https://web.archive.org/web/20151210223620/https://www.ameslab.gov/mpc/video |archive-date=December 10, 2015|title=Video of an AB<sub>5</sub> intermetallic compound solidifying/freezing}}

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[[Category:Intermetallics| ]]