Permanent magnets based on Sm(Co, Cu, Fe) z

It is known that copper-hardened magnets can be prepared from alloys lying between the 1:5 and 2:17 phases. We show that good magnetic properties are only obtained within a limited region of the phase space, in material which has been equilibrated at temperatures of the order 1200°C and then given a second treatment at about 800°C. Such materials contain two phases which form at the higher temperature and which are metastable at low temperatures. Decomposition of the phases adversely affects the magnetic properties. Small additions of iron enhance both remanence and coercivity provided no FeCo precipitation occurs; the microstructural requirements are otherwise identical to iron-free materials.