Anintermetallic (also called an intermetallic compound, intermetallic alloy, ordered intermetallic alloy, and a long-range-ordered alloy) is a type of metallicalloy that forms a solid-state compound exhibiting defined stoichiometry and ordered crystal structure.
Although the term "intermetallic compounds", as it applies to solid phases, has been in use for many years, its introduction was regretted, for example by Hume-Rothery in 1955.[1]
Definitions
Research definition
Schulze in 1967[2] 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. Under this definition, the following are included:
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.
The term intermetallic is used[3] to describe compounds involving two or more metals such as the cyclopentadienyl complexCp6Ni2Zn4.
B2
AB2 intermetallic compound has equal numbers of atoms of two metals such as aluminium and iron.[4]
Properties and applications
Inter-metallic compounds are generally brittle and have high melting points. They often 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 also display desirable magnetic, superconducting and chemical properties, due to their strong internal order and mixed (metallic and covalent/ionic) bonding, respectively. Inter-metallic have given rise to various novel materials developments. Some 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 also attracted interest for turbine blade applications, while the latter is also used in very small quantities for grain refinementoftitanium alloys. Silicides, inter-metallic involving silicon, are utilized as barrier and contact layers in microelectronics.[5]
German type metal is described as breaking like glass, not bending, softer than copper but more fusible than lead.[7] The chemical formula does not agree with the one above; however, the properties match with an intermetallic compound or an alloy of one.
^S.P. Murarka, Metallization Theory and Practice for VLSI and ULSI. Butterworth-Heinemann, Boston, 1993.
^Milton Ohring, Materials Science of Thin Films, 2nd Edition, Academic Press, San Diego, CA, 2002, p. 692.
^[1]Type-pounding The Penny Cyclopædia of the Society for the Diffusion of Useful Knowledge By Society for the Diffusion of Useful Knowledge (Great Britain), George Long Published 1843
