Hot-pressed and die-upset Pr-Co magnets produced from mechanically activated alloys

Anisotropic die-upset PrCo5-based magnets were produced by hot pressing and subsequent die-upsetting of alloy powders activated by high-energy ball milling. In addition to the PrCo5 major phase the magnets contained Pr2Co17, even when prepared from a stoichiometric 1:5 alloy. Hard magnetic properties can be improved by partial Sm substitution for Pr and partial Cu substitution for Co. A higher cobalt/rare-earth ratio as well as the addition of Fe was found to be unfavorable for the deformation-induced anisotropy. The largest values of remanence, intrinsic coercivity and maximum energy product in hot-pressed magnets were obtained for Pr0.7Sm0.3Co5.5 (7.8 kG, 14.1 kOe and of 13.1 MGOe) and in die-upset magnets for Pr0.9Sm0.1(Co0.98Cu0.02)5 (9.2 kG, 10.5 kOe and 16.7 MGOe).