aluminumnickelcobalt

Aluminumnickelcobalt, usually written as aluminum–nickel–cobalt or AlNiCo, is a family of permanent magnet alloys based on iron with aluminum, nickel, and cobalt as the principal alloying elements. The name reflects these core constituents, and many formulations also contain copper and titanium to refine microstructure. AlNiCo magnets were among the earliest commercially used permanent magnets and have remained in use for specific high-temperature applications.

Composition and processing: Typical formulations comprise iron as the base (roughly 50–70%), aluminum about 5–15%, nickel about 10–30%, and cobalt about 5–20%, with small additions of copper and titanium. They can be produced by casting or powder metallurgy and are often heat-treated to develop magnetic anisotropy in certain grades. Isotropic grades magnetize in any direction, while anisotropic grades are oriented during fabrication for higher energy products.

Properties: AlNiCo magnets feature high thermal stability and a high Curie temperature, allowing operation at elevated temperatures. They offer a moderate magnetic energy product and low coercivity compared with rare-earth magnets, but excellent machinability, formability, and corrosion resistance when properly finished. Their mechanical robustness and ability to be cast into complex shapes are notable advantages.

Applications and history: Developed in the early 20th century, AlNiCo magnets were widely used in loudspeakers, microphones, telecommunication equipment, and guitar pickups. While largely superseded by neodymium and samarium–cobalt magnets for many applications, AlNiCo remains in use in specialty roles that require high temperature stability, simple casting, or compatibility with older equipment.