AlNiCo

AlNiCo refers to a family of permanent magnets made primarily from aluminum, nickel, cobalt, and iron, with smaller amounts of other elements such as copper or titanium in certain grades. The name reflects the principal constituents of the alloy.

Historically developed in the 1930s, AlNiCo magnets were among the earliest commercially produced permanent magnets and remained widely used through the mid-20th century. They are produced in isotropic forms, which can be magnetized in any direction, and anisotropic forms, which are aligned during fabrication to achieve higher magnetic performance. Anisotropic grades typically require a strong magnetic field and heat treatment to acquire their preferred orientation and higher energy product.

Chemically, AlNiCo alloys have variable compositions but are dominated by iron, with significant nickel and cobalt, and smaller amounts of aluminum. Some grades include copper and titanium to modify microstructure and harden the material. The magnetic properties depend on the exact composition and processing, but in general AlNiCo magnets offer good temperature stability and corrosion resistance, and they can operate at relatively high temperatures compared with other magnets. Their energy product (a measure of strength) is lower than that of modern rare-earth magnets, and some grades have lower coercivity, making them more susceptible to demagnetization in strong opposing fields.

Common applications include loudspeakers, guitar and bass pickups, microphones, and various sensing or electromechanical devices where high-temperature performance or non-rare-earth composition is advantageous. While largely supplanted for many new designs by NdFeB and SmCo magnets, AlNiCo remains valued for its temperature stability, machinability, and resistance to corrosion in specific uses.