Permendur is a

cobalt Cobalt is a chemical element with the symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, pr ...

iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...

soft

ferromagnetic Ferromagnetism is a property of certain materials (such as iron) which results in a large observed magnetic permeability, and in many cases a large magnetic coercivity allowing the material to form a permanent magnet. Ferromagnetic materials ...

alloy An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductility, ...

with equal parts of cobalt and iron which is notable for its high

magnetic saturation Seen in some magnetic materials, saturation is the state reached when an increase in applied external magnetic field ''H'' cannot increase the magnetization of the material further, so the total magnetic flux density ''B'' more or less levels off ...

level. Its saturation flux density of around 2.4 tesla is the highest of any commercially available metal. Coupled with its low

coercivity Coercivity, also called the magnetic coercivity, coercive field or coercive force, is a measure of the ability of a ferromagnetic material to withstand an external magnetic field without becoming demagnetized. Coercivity is usually measured in ...

and

core loss A magnetic core is a piece of magnetic material with a high magnetic permeability used to confine and guide magnetic fields in electrical, electromechanical and magnetic devices such as electromagnets, transformers, electric motors, generators, in ...

es, its high saturation and permeability makes Permendur useful as magnetic cores in

transformer A transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple circuits. A varying current in any coil of the transformer produces a varying magnetic flux in the transformer' ...

electric generator In electricity generation, a generator is a device that converts motive power (mechanical energy) or fuel-based power (chemical energy) into electric power for use in an external circuit. Sources of mechanical energy include steam turbines, gas ...

s and other electrical equipment. The advantage of high saturation in a magnetic core is that it can function at higher

magnetic field A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...

strengths, so the core can be smaller and lighter for a given magnetic flux and power level. Permendur is used for magnetic cores and pole pieces in lightweight transformers and electric motors used in aircraft. The alloy was invented in 1929 by Gustav Elmen at

Bell Telephone Laboratories Nokia Bell Labs, originally named Bell Telephone Laboratories (1925–1984), then AT&T Bell Laboratories (1984–1996) and Bell Labs Innovations (1996–2007), is an American industrial research and scientific development company owned by mult ...

. Various formulations are sold under different trade names. Cobalt-iron alloys like permendur have very high

Curie temperature In physics and materials science, the Curie temperature (''T''C), or Curie point, is the temperature above which certain materials lose their permanent magnetic properties, which can (in most cases) be replaced by induced magnetism. The Cur ...

s so they can function magnetically at high temperatures at which other ferromagnetic materials lose their magnetic properties. They are harder and less

ductile Ductility is a mechanical property commonly described as a material's amenability to drawing (e.g. into wire). In materials science, ductility is defined by the degree to which a material can sustain plastic deformation under tensile stres ...

than many other iron alloys and so are harder to fabricate, but have superior mechanical strength. Most permendur alloys require

heat treatment Heat treating (or heat treatment) is a group of industrial, thermal and metalworking processes used to alter the physical, and sometimes chemical, properties of a material. The most common application is metallurgical. Heat treatments are also ...

after fabrication to attain the best magnetic properties. The most important alloys are *''Permendur 2V'' (''Vanadium Permendur'', ''Permendur 49''): Invented by White and Wahl in 1932, it is approximately 49% cobalt, 49% iron and 2%

vanadium Vanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery-grey, malleable transition metal. The elemental metal is rarely found in nature, but once isolated artificially, the formation of an oxide layer ( pas ...

. The vanadium improves ductility and workability. *''Supermendur'' (''Hiperco 50''): Invented by Gould and Wenny in 1957, it has similar composition to Permendur 49 but is grain-oriented so it has a square hysteresis loop and much lower

es, for better performance in transformers. Current formulations include trace amounts of

niobium Niobium is a chemical element with chemical symbol Nb (formerly columbium, Cb) and atomic number 41. It is a light grey, crystalline, and ductile transition metal. Pure niobium has a Mohs hardness rating similar to pure titanium, and it has sim ...

silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic tab ...

and

manganese Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy use ...

to improve cold-forming properties. The coercivity can be controlled by varying the vanadium concentration. Equiatomic cobalt-iron alloys with more vanadium than permendur, 2-5%, are called ''Remendur''. This is a medium-coercivity magnet material which bridges the gap between Permendur and

Vicalloy Vicalloy is a family of cobalt-iron-vanadium wrought ferromagnetic alloys which have high coercivity and are used to make permanent magnets and other magnetic components. Vicalloy is precipitation hardened and can be formed by a number of cold ...

cobalt-iron magnets with 8-15% vanadium.

References

Cobalt alloys {{Alloy-stub