R-Fe-B type magnet powder, sintered magnets therefrom and preparation process

The magnetic powder employed for the manufacture of sintered magnets of the RE-T-B class, where RE denotes at least one rare earth, T at least one transition element and B boron, consists of the mixture of 2 powders (A) and (B): a) the powder (A) consisting of grains of RE2T14B tetrahedral structure, T being essentially iron with Co/Fe < 8 % being also capable of containing up to 0.5 % Al, up to 0.05 % Cu and up to 4 % in all of at least one element from the group consisting of V, Nb, Hf, Mo, Cr, Ti, Zr, Ta, W and of the unavoidable impurities, with a Fisher particle size of between 3.5 and 5 mu m; b) the powder (B) being rich in RE and containing Co, having the following composition by weight: RE 52-70 %, including at least 40 % (in absolute value) of one (or more) light rare earth(s) chosen from the group consisting of La, Ce, Pr, Nd, Sm and Eu; Co 20-35 %; Fe 0-20 %; B 0-0.2 %; Al 0.1-4 %; and unavoidable impurities, with a Fisher particle size of between 2.5 and 3.5 mu m. The powder (B) may be obtained by mixing a RE-rich powder (C) containing Co with a B-rich powder (D). La poudre magnétique utilisée pour la fabrication d'aimants frittés de la famille des TR-T-B, où TR désigne au moins une terre rare, T au moins un élément de transition et B le bore, est constituée par le mélange de 2 poudres (A) et (B) : a) la poudre (A) étant constituée de grains de structure quadratique TR2T14B, T étant essentiellement du fer avec Co/Fe