Alnico (Aluminum-Nickel-Cobalt) permanent magnetic material was developed in the 1930s. It is one of the earliest permanent magnetic materials in history and is an alloy composed of aluminum, nickel, cobalt, iron, and trace amounts of other metallic elements. Before the discovery of rare-earth permanent magnets in the 1970s, Alnico alloys were the strongest permanent magnetic materials. However, with the subsequent emergence of ferrite and rare-earth permanent magnets, Alnico permanent magnets were gradually replaced in many applications.

Classification of Alnico

Alnico permanent magnets have low mechanical strength, high hardness, brittleness, and poor machinability. Therefore, they cannot be used as structural components, and only limited grinding or electrical discharge machining can be performed during processing. Forging and other mechanical processing methods are not suitable.

Alnico is primarily produced through casting, but it can also be made into sintered magnets corresponding to cast magnets using powder metallurgy methods, although their performance is slightly lower.

The production process of cast Alnico includes ingredient preparation, melting, casting, heat treatment, performance testing, machining, inspection, and packaging. The production process of sintered Alnico includes ingredient preparation, powder production, pressing, sintering, heat treatment, performance testing, machining, inspection, and packaging.

Performance and Applications of Alnico Magnets

The advantages of Alnico magnets include a high remanence (up to 1.35T), but their drawback is very low coercivity (typically less than 160kA/m) and a nonlinear demagnetization curve. As a result, Alnico magnets are easy to magnetize and equally easy to demagnetize. When designing and manufacturing devices using Alnico magnets in magnetic circuits, special attention must be paid to their unique characteristics. The magnets must be magnetically stabilized in advance, and during use, they must not come into contact with any ferromagnetic materials to prevent localized irreversible demagnetization or distortion of magnetic flux density distribution.

Among permanent magnetic materials, cast Alnico has the lowest reversible temperature coefficient. Alnico magnets have good temperature stability and aging stability, making them suitable for making instruments, meters, electric motors, audio devices, magnetic machinery, and more.