Alnico magnets, composed of primarily aluminum (Al), nickel (Ni), and cobalt (Co), were developed in the 1940's. This class of magnet remains a preferred material because of its excellent temperature stability, high magnetic flux density, and resistance to corrosion.
Alnico magnets are manufactured through a casting or sintering process. The casting process allows for the magnet to be manufactured into intricate and complex shapes. Sintered Alnico is made from a powdered mixture of ingredients that are pressed into a die under tons of pressure. The Sintering process allows for the magnets to be manufactured to tighter tolerances and higher mechanical strength.
Cast Alnico is manufactured by pouring a molten metal alloy into a mold and then further processing it through various heat-treat cycles.
The resulting magnet has a dark gray exterior appearance, and may have a rough surface.Machined surfaces have a shiny appearance similar to steel. It permits high temperature operation.
Alnico 8 and Alnico 9 has a higher coercive force and is usually used in disc shapes.