Effects of a partial substitution of Fe by Mo and Mo plus Co on the structure and magnetic properties of Nd8.4Fe87.1B4.5 alloys prepared by mechanical alloying

The effects of the addition of Mo alone and the addition of Mo pins Co an t he structure and magnetic properties of mechanically alloyed Nd8.4Fe87.1B4. 5 alloy were studied. Both the addition of Mo alone and the addition of Mo plus Co result in an increase in the Curie temperatures of the hard phases. The addition of Mo alone, especially for the 1.6 at% Mo-added case, result s in the improvement of the intrinsic coercivity H-0(c) and the maximum mag netic energy product (BH)(max). The addition of Mo alone results in refinem ent of alpha-Fe grains but in coarsening of the hard grains. The addition o f both Co and Mo can both refine the soft grains and inhibit the trend of c oarsening of the hard grains due to the addition of Mo alone. The best magn etic properties: mu(0)H(c) = 0.58 T (5.8 kOe), J(r) = 1.04 T (10.4 kG), (BH )(max) = 113.8 kJ m(-3) (14.3 MGOe), J(r)/J(s) = 0.68, are achieved for the Nd8.4Fe80.4Co5.6Mo1.1B4.5 alloy. (C) 2000 Elsevier Science S.A. All rights reserved.