An Alnico magnet is a type of permanent magnet made from a combination of aluminum, nickel, and cobalt, along with small amounts of other elements like iron, copper, and sometimes titanium. The name "Alnico" is derived from the first letters of these constituent elements.
Alnico magnets were among the first widely used types of permanent magnets and are known for their strong magnetic properties, high temperature stability, and resistance to demagnetization. They were developed in the 1930s and have been used in a wide range of applications since then.
Here are some key characteristics and uses of Alnico magnets:
1. Composition: Alnico magnets are typically composed of approximately 8-12% aluminum, 15-25% nickel, 5-24% cobalt, and smaller amounts of iron, copper, and other elements. These elements are alloyed together and then subjected to heat treatment to create a crystalline microstructure that provides their magnetic properties.
2. Strong Magnetic Field: Alnico magnets offer strong magnetic fields and exhibit excellent magnetic strength, making them suitable for various applications that require powerful magnets.
3. High Temperature Stability: One of the significant advantages of Alnico magnets is their ability to maintain their magnetic properties at high temperatures. They have a high Curie temperature (temperature at which they lose their magnetism) compared to other types of magnets.
4. Resistant to Demagnetization: Alnico magnets are relatively resistant to demagnetization caused by external magnetic fields, making them suitable for applications where stability is important.
5. Shapes and Sizes: Alnico magnets can be manufactured in various shapes, including horseshoe, bar, rod, and cylindrical shapes, to suit different application needs.
6. Applications: Alnico magnets have been used in a wide range of applications, including electric motors, generators, sensors, loudspeakers, guitar pickups, medical devices, measuring instruments, and various industrial and scientific equipment.
7. Magnetic Grades: Alnico magnets come in different grades, often designated by letters like Alnico 2, Alnico 5, and Alnico 8. These grades have slightly different magnetic properties, including strength and coercivity, to suit different applications.
8. Brittle Nature: Alnico magnets are relatively brittle and can be prone to chipping or breaking if subjected to mechanical stress or impacts.
9. Machinability: Alnico magnets can be machined and drilled using diamond tools, which can be advantageous for applications that require specific shapes or features.
While Alnico magnets have been widely used historically, other types of magnets like neodymium (NdFeB) magnets and samarium cobalt (SmCo) magnets have gained prominence due to their even stronger magnetic properties and greater resistance to demagnetization. However, Alnico magnets are still preferred in certain applications where their temperature stability and durability are key considerations.