Iron-nickel-aluminium alloys (alnicos)
Permanent magnets

These alloys, known since the 1930s, marked a clear advance in the field of permanent magnets at a time when only martensitic hard steels were used. The starting point was the NiAlFe ₂ alloy, whose properties were considerably improved by a number of additions such as cobalt and titanium, as well as by heat treatments.

Different families of magnets can be obtained from these alloys:

• isotropic alloys ;

• anisotropic alloys ;

• alloys with directed or columnar crystallization ;

• sintered alloys.

These magnets are prepared by melting and casting to produce relatively fragile, high-hardness parts. Machining is carried out by diamond grinding or...