Sintering and Casting AlNiCo Magnet

Alnico permanent magnet materials can't be designed as structural parts due to the features of low mechanical strength, high hardness, brittleness, and poor machinability. Only a little grinding or EDM can be used during processing, other methods like forging and other machining can't be used.

AlNiCo is mainly produced by casting method. In addition, powder metallurgy can also be used to make sintered magnets, which has slightly lower performance. Cast AlNiCo can be processed into different sizes and shape while sintered AlNiCo products are mainly small-sized. And the workpieces of sintered AlNiCo have better dimensional tolerances, the magnetic properties are a little bit lower but the machinability is better.

The advantage of AlNiCo magnets is high remanence (up to 1.35T), but the shortage is that the coercive force is very low (usually less than 160kA/m), and the demagnetization curve is non linear, so AlNiCo is a magnet easy to be magnetized and also easy to be demagnetized. When magnetic circuit designing and device manufacturing, special attention should be paid and the magnet must be stabilized in advance. In order to avoid partial irreversible demagnetization or distortion of magnetic flux density distribution, it is strictly forbidden to contact with any ferromagnetic substances during use.

Cast AlNiCo permanent magnet has the lowest reversible temperature coefficient among the permanent magnet materials, the working temperature can reach up to 525°C, and the Curie temperature to 860°C, which is the permanent magnet material with the highest Curie point. Due to good temperature stability and aging stability, AlNiCo magnets are well applied in motors, instruments, electroacoustic devices, and magnetic machinery, etc.