Intermetallic

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Type of metallic alloy

title: "Intermetallic" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["intermetallics"] description: "Type of metallic alloy" topic_path: "general/intermetallics" source: "https://en.wikipedia.org/wiki/Intermetallic" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Type of metallic alloy ::

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

The term "intermetallic compounds" applied to solid phases has long been in use. However, Hume-Rothery argued that it misleads, suggesting a fixed stoichiometry and a clear decomposition into species.

Definitions

Research definition

In 1967 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. This definition includes:

The definition of metal includes:

Homogeneous and heterogeneous solid solutions of metals, and interstitial compounds such as carbides and nitrides are excluded under this definition. However, interstitial intermetallic compounds are included, as are alloys of intermetallic compounds with a metal.

Common use

In common use, the research definition, including post-transition metals and metalloids, is extended to include compounds such as cementite, Fe3C. These compounds, sometimes termed interstitial compounds, can be stoichiometric, and share properties with the above intermetallic compounds.

Complexes

The term intermetallic is used to describe compounds involving two or more metals such as the cyclopentadienyl complex Cp6Ni2Zn4.

B2

::figure[src="https://upload.wikimedia.org/wikipedia/commons/7/7a/Al-Ni_(B2_structure).png" caption="Al-Ni]] B2 structure (lattice parameter: 2.86 A) viewed from [100], [110], [111], and [112] directions."] ::

A B2 (also known as cesium chloride structure type) intermetallic compound has equal numbers of atoms of two metals, such as aluminium-iron, and aluminium-nickel, arranged as two interpenetrating simple cubic lattices of the component metals.

Properties

Intermetallic compounds are generally brittle at room temperature and have high melting point, though many also exhibit metallic conductivity or semiconducting behavior depending on the degree of covalent bonding. Cleavage or intergranular fracture modes are typical of intermetallics due to limited independent 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. 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 magnetic and chemical properties, due to their strong internal order and mixed (metallic and covalent/ionic) bonding, respectively. Intermetallics have given rise to various novel materials developments. ::data[format=table title="Physical properties of intermetallics"]

Intermetallic CompoundMelting TemperatureDensityYoung's Modulus (GPa)
FeAl1250–14005600263
Ti3Al16004200210
MoSi220206310430
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Applications

Examples include alnico and the hydrogen storage materials in nickel metal hydride batteries. Ni3Al, which is the hardening phase in the familiar nickel-base super alloys, 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 alloys. Silicides, intermetallics involving silicon, serve as barrier and contact layers in microelectronics. Others include:

The unintended formation of intermetallics can cause problems. For example, intermetallics of gold and aluminium can be a significant cause of wire bond failures in semiconductor devices and other microelectronics devices. The management of intermetallics is a major issue in the reliability of solder joints between electronic components.

Intermetallic particles

Main article: Intermetallic particle

Intermetallic particles often form during solidification of metallic alloys, and can be used as a dispersion strengthening mechanism.

History

Examples of intermetallics through history include:

German type metal is described as breaking like glass, without bending, softer than copper, but more fusible than lead. The chemical formula does not agree with the one above; however, the properties match with an intermetallic compound or an alloy of one.

References

Sources

References

  1. (January 2015). "The science and engineering of materials".
  2. Panel On Intermetallic Alloy Development, Commission On Engineering And Technical Systems. (1997). "Intermetallic alloy development : a program evaluation". National Academies Press.
  3. Soboyejo, W. O.. (2003). "Mechanical properties of engineered materials". Marcel Dekker.
  4. Hume-Rothery, W.. (1955). "Electrons, atoms, metals and alloys". Louis Cassier Co., Ltd.
  5. G. E. R. Schulze: Metallphysik, Akademie-Verlag, Berlin 1967
  6. (10 March 1958). "Complex alloy structures regarded as sphere packings. I. Definitions and basic principles". Acta Crystallographica.
  7. {{Cotton&Wilkinson6th
  8. (7 February 2015). "Wings of steel: An alloy of iron and aluminium is as good as titanium, at a tenth of the cost". The Economist.
  9. Soboyejo, W. O.. (2003). "Mechanical properties of engineered materials". Marcel Dekker.
  10. Murarka, S.P.. (June 1993). "Metallization: theory and practice for VLSI and ULSI". Choice Reviews Online.
  11. "The Art of War by Sun Zi: A Book for All Times". [[China Today]].
  12. Long, George. (1843). ["The Penny Cyclopædia of the Society for the Diffusion of Useful Knowledge"]({{google books). C. Knight.

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intermetallics