Optimisation of the processing of Nd-Fe-B with dysprosium addition

Magnets based on Nd(16)Fe(76)B(8) with DyH(3) additions have been sintered at different temperatures. The magnetic properties, microstructure and compositions have been examined. Details of progress of Dy entering the hard matrix phase (phi) is observed and an evolution mode of the relevant sintering process is proposed, observed and reported in the present work. Hydrogen absorption and desorption of the magnets were examined by HDTA. The optimum sintering temperature for these magnets has been established. Microstructural and EDX examinations revealed that a relatively Dy-rich phase formed in the Nd-rich grain boundary phase and this slowed down the substitution of Nd by Dy in the Nd(2)Fe(14)B matrix phase, possibly enhancing local coercivity without excessive attenuation of the remanence. Hydrogen Decrepitation (HD) occurred as sintered RE-Fe-B magnets were exposed to hydrogen at room temperatures. (C) 2009 Elsevier B.V. All rights reserved.