1. Cast alnico magnets that are made by pouring melted alnico into a mold. The solidified material is rough ground and then heat treated and cooled. The material is either anisotropic (treated in a magnetic field) or isotropic (treated outside a magnetic field). After treatment the material is ground to specific tolerances and magnetized.
   
2. Sintered alnico magnets are made from a powdered mixture of ingredients that are pressed into a die under tons of pressure. They are then sintered in a hydrogen atmosphere and cooled in an anisotropic or isotropic environment.
   

AlNiCo magnets have very stable temperature properties and they are great for high heat applications. Its temperature coefficient is very low, so the change of magnetic properties is low under high temperature. The maximum working temperature can be as high as 550 degree Celsius or 1022 degree Fahrenheit.  
AlNiCo magnets have good corrosion resistance characteristic . No coating is needed for surface protection.

The coercive force of AlNiCo magnets is very low , so it can be easily effected by reverse magnetic force, impact or touched by iron. This means that they can be easily demagnetized by external influences. AlNiCo magnets should not be stored and packed with the same poles opposing each other. open circuit, the ration of length/diameter (L/D) should be at least 4: 1. With shorter length, AlNiCo magnets are unstable in open circuit.  

AlNiCo magnets are hard and brittle, they are not recommended for conventional machining.

Compared to ceramic magnets, they have Higher residual induction and energy product.

Compared to rare earth magnets, they have lower coercive force, therefore they can be easily demagnetized.

Applications:


The AlNiCo (Aluminum, Nickel, Cobalt) magnets were introduced in the 1930's. Due to their excellent temperature stability, high residual induction, relatively high energies and strong resistance to corrosion, They are widely used for motor,sensor,separator, loudspeaker, Electronic ignition systems, generators, vending machines, hand tools, magnetic reed switches, volt-amp meters, medical instruments and other magnetic applications.



Alnicos are precipitation-hardened alloys requiring special heat treatment techniques. The raw materials are Cobalt, Nickel, Copper, Aluminum and Iron. Titanium, silicon, etc. are added in certain proportions. The raw materials in their purest form are melted in medium frequency induction furnaces and castings are made using conventional sand or shell moulds. The heat treatment consists of heating the alloy in furnace to well above its curie point, and holding it at that temperature for some time. This is followed by controlled cooling after which the castings are reheated and held for a long period at a temperature of about 600°C. This ageing process increases the coercive force and the energy product. Finally, the castings are ground to obtain close dimensional tolerances whenever necessary and inspected for physical and magnetic accuracy.



High quality Cast Alnico magnet

Cast Alnico 5 is the most commonly used of all the cast Alnico's .It combines high indications with a high energy product of 5 MGOe or more and is used extensively in rotation machinery, communications, meters and instruments, sensing devices and holding applications. The higher resistance to demagnetization(coercive force) of Alnico 8,cobalt content to 35%,allows this material to function well for short lengths or for length to diameter ratios of less than 2 to 1.
The Characteristics of Alnico Magnet: