A STUDY OF THE EFFECTS OF THE ADDITION OF VARIOUS AMOUNTS OF CU TO SINTERED ND-FE-B MAGNETS

Magnets according to the formula (Nd16Fe76B8)(1-x)Cu-x (0.1 less than or equal to x less than or equal to 1.5) have been produced by adding Cu powder to hydrogen decrepitated Nd-Fe-B powder prior to ball millin g, as part of the powder metallurgy processing route. Microstructural examination of the sintered magnets revealed increasing porosity with increasing Cu content. Heat treating the sintered magnets at 500 degre es C increased the coercivities of all of the magnets and in particula r the magnet with 0.25 at.% Cu, which was found to be the optimum addi tion. This magnet exhibited a steady increase in coercivity on anneali ng, without any detrimental effect on the remanence. This enabled a ma gnet to be produced with a remanence of 1295 mT, an intrinsic coercivi ty of 1030 kA m(-1) and a maximum energy product of similar to 340 kJ m(-3) (similar to 43 MG Oe). (C) 1997 Elsevier Science S.A.