Die‐upset PrCo₅‐type magnets: Enhanced coercivities Available to Purchase

Rare‐earth–cobalt alloys have been melt spun, yielding ribbons whose major phase was the hexagonal PrCo₅ phase. Fully dense hot‐pressed magnets with essentially isotropic magnetic properties have been formed by consolidating the ribbons at high temperatures and pressures. The hot‐pressed precursor was then subjected to hot deformation or die upsetting, thereby inducing partial alignment of the c axis along the press direction. The resulting magnets had remanences approaching ∼75% of the saturation magnetization of the hexagonal PrCo₅ phase. Three approaches were used to optimize the coercivity of the die‐upset magnets: (i) replacing small amounts of cobalt with carbon; (ii) partially substituting samarium for the praseodymium; and (iii) high‐temperature heat treatment followed by a thermal quench. Coercivities near ∼20 kOe were achieved with thermally quenched die‐upset (Pr_0.6Sm_0.4)₁₈Co₈₁C magnets, while maintaining remanences above 8 kG.