AlNiCo Magnets

AlNiCo, an abbreviation for Aluminum-Nickel-Cobalt, is a non-rare earth metallic permanent magnet material primarily composed of aluminum (Al), nickel (Ni), cobalt (Co), and iron (Fe). Small amounts of alloying elements such as Titanium (Ti), Niobium (Nb), and Copper (Cu) are also incorporated to promote the growth of the needle phase and thereby enhance coercivity. AlNiCo magnets once dominated the permanent magnet industry until the advent of rare earth permanent magnets. Although their production is limited today, the discovery and development of AlNiCo magnets marked a crucial milestone in the evolution of permanent magnetic materials.

It’s worth noting that AlNiCo magnets are susceptible to demagnetization and are best utilized in closed magnetic circuits or with a high length-to-diameter (L/D) ratio. In addition to common applications like loudspeakers, sensors, guitar pickups, magnetic chucks, or magnetic lifters, AlNiCo magnets continue to serve in certain specialty applications owing to their unmatched temperature stability.

Understanding the magnetic properties of AlNiCo magnets is essential for selecting the appropriate grade for specific applications. AlNiCo magnets feature various trade names for designating their grades, such as Columax, Alcomax, Hycomax, Ticonal, and others. Most people are still familiar with AlNiCo magnets through MMPA class names, including Alnico 2, Alnico 3, Alnico 5, Alnico 5DG, Alnico 8, Alnico 8HC, and Alnico 9. AlNiCo grades vary in cobalt content, ranging from zero (Alnico 3) to 40% (Alnico 8). Lower grades (2, 3, and 4) are unoriented, with isotropic magnetic properties that result in relatively low magnetic output. In contrast, anisotropic grades (5, 6, 8, and 9) are designed to provide high magnetic output in a specific direction.

The Chinese nomenclature system designates cast AlNiCo magnets with the prefixes LNG or LNGT, followed by a number. The letters LNGT represent the Chinese phonetic abbreviations for aluminum, nickel, cobalt, and titanium, respectively. The subsequent number indicates the minimum value of the maximum energy product (BH)max in the SI unit of kJ/m³. The letter J appended at the end signifies high coercivity. For sintered AlNiCo magnets, the letter F is the acronym for sintered powder material in the Chinese phonetic alphabet, leading to prefixes like FLNG or FLNGT.