What Are Alnico Magnets

Types of Alnico Magnets

Alnico magnets are classified into different grades based on their composition and magnetic properties:

Alnico 2: Offers a good balance of magnetic strength and temperature stability.

Alnico 5: Provides strong magnetic strength and is the most widely used grade.

Alnico 8: Features enhanced magnetic strength and temperature stability compared to Alnico 5.

Alnico 9: Offers the highest coercivity and is used in applications requiring very strong magnetic fields.

Composition and Manufacturing

Alnico magnets are composed primarily of aluminium, nickel, and cobalt, along with iron and small amounts of other elements such as copper and titanium. The exact composition can vary, but typical formulations include:

  • Aluminum (Al): Provides stability and enhances corrosion resistance.
  • Nickel (Ni): Contributes to magnetic strength and temperature stability.
  • Cobalt (Co): Increases the magnetic strength and coercivity (resistance to demagnetization).
  • Iron (Fe): Acts as a stabilizer and provides structure to the magnet.
  • Other elements (e.g., copper, titanium): Added in small amounts to improve specific properties.

Alnico magnets are manufactured through a casting or sintering process:

  1. Casting: Molten alloy is poured into moulds to form desired shapes, allowing for intricate designs and precise tolerances.
  2. Sintering: Powdered alloys are compacted in a press and then heated in a furnace to fuse the particles, forming solid magnets.

Properties

  • Alnico magnets are known for their strong magnetic fields, typically stronger than ferrite magnets but weaker than neodymium magnets.
  • They have a high maximum operating temperature, typically around 450-550°C, making them suitable for high-temperature applications where other magnets may demagnetize.
  • Alnico magnets have high coercivity, meaning they are resistant to demagnetization and can retain their magnetic properties over long periods.
  • They exhibit good resistance to corrosion, although surface oxidation can occur over time.
  • Alnico magnets are relatively dense compared to other types of magnets, which can affect their weight and size in applications.