Microstructure refinement and magnetic property enhancement of nanocomposite Pr2Fe14B/alpha-Fe magnets by small substitution of M for Fe (M=Cr, Nb, Ti and Zr)

A comprehensive study on the effect of various substitutions of M on the ma gnetic and structural properties of melt-spun nanocomposite Pr8Fe84M6. (M=C r, Nb, Ti and Zr) magnets has been performed with the aim of refining the m icrostructure and therefore enhancing the hard magnetic properties. It has been found that magnetic properties are improved by all the substitutions. The largest enhancement is obtained in Nb substituted Pr8Fe86B6 magnets whe re a coercivity of 6.5 kOe and a maximum energy product of 17.9 MGOe have b een obtained, as compared to the coercivity of 4.3 kOe and the energy produ ct of 9.1 MGOe in the Pr8Fe86B6 magnet. Microstructure studies revealed a f iner and more uniform 2:14:1 /ot-Fe nanoscale microstructure with M substit utions. The most uniform microstructure with the smallest average grain siz e of 10-20 nm is developed in the Nb substituted magnets. The enhancement o f magnetic properties by M substitution is believed to be due to the micros tructure refinement which leads to an enhanced exchange coupling between Pr 2Fe14B and alpha -Fe. (C) 2001 Elsevier Science BY All rights reserved.