Sintered AlNiCo Magnets

AlNiCo magnets are manufactured using either a sintering process or, more commonly, a casting process, each suited to specific applications. Sintered AlNiCo magnets are produced by pressing a mixture of fine metal powders into a die that closely approximates the final shape, followed by sintering the compacted powder to form a solid magnet. Although sintered AlNiCo magnets exhibit slightly lower magnetic performance compared to their cast counterparts and are thus not as widely used, they are particularly well-suited for small-to-medium sized (less than 28 grams), thin, light, and special shaped magnets.

Sintered AlNiCo magnets offer several advantages, including high dimensional accuracy and the elimination of additional machining steps. They also demonstrate slightly better mechanical properties and machinability. Compared to cast AlNiCo magnets, sintered AlNiCo magnets provide higher material utilization rates, reduced composition segregation, and lower fluctuations in magnetic performance during mass production.

AlNiCo magnets have 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 sintered AlNiCo magnets with the prefixes FLNG or FLNGT, followed by a number. The letters FLNGT stand for the Chinese phonetic abbreviations for sintered powder material, Aluminum, Nickel, Cobalt, and Titanium, respectively. The following number represents the minimum value of the maximum energy product (BH)max in the SI unit of kJ/m³. A letter J appended at the end indicates high coercivity.