Effect of Cu and Ti additions on the microstructures and magnetic properties of Nd8Fe86B6 nanocomposite magnets

The microstructure and magnetic properties of Nd8Fe86B6 nanocomposite magnets with combined Cu and Ti additions prepared by melt spinning have been investigated. The results show that Cu can enhance the nucleation kinetics of alpha-Fe phase, while Ti can hinder the crystallization kinetics of alpha-Fe phase. For pure ternary NdFeB and a single Cu addition NdFeBCu ribbons, the alpha-Fe phase precipitates directly from amorphous and its grains grow quickly during crystallization. But for the NdFeBCuTi ribbons with combined Cu and Ti additions, a metastable hexagonal phase with TbCu7-type structure is formed prior to alpha-Fe and quickly decomposed to Nd2Fe14B and alpha-Fe phases during crystallization. At the same time, the growth of alpha-Fe grains is suppressed, which is propitious to form the more uniform microstructure with fine soft alpha-Fe grains and enhance the magnetic properties. The optimal magnetic properties H-J(c) = 4.6 kOe, sigma(r) = 102 emu/g, (BH)(max) = 13 MGOe can be obtained after annealed at the temperature of 650degreesC for 10 min. (C) 2002 Elsevier Science B.V. All rights reserved.