Structure and magnetic properties of Nd2(Fe,Co,Al,Cr)14B/α-Fe nanocomposite magnets

The structure, magnetic properties and corrosion behaviour of two-phase nanocomposite Nd-2(Fe,Co,Al,Cr)(14)B/alpha-Fe-type magnets, which have tetragonal/cubic Nd2Fe14B/alpha-Fe structure, have been investigated. The magnetic hardening was achieved by high-energy ball-milling (HEBM) of the Nd2Fe,,B-type hard magnetic phase with different vol.% of alpha-Fe as soft magnetic phase, followed by annealing. Fully dense Nd-2(Fe,Co,Al,Cr)(14)B/alpha-Fe type magnets have been produced by hot pressing. Magnets with good corrosion resistance as well as high temperature stability have been produced. The corrosion resistance is improved in the case of Co-, Al-, Cr-doped nanocomposite magnets with a volume fraction of the soft magnetic phase of 37.5 vol.%. Effective protection against corrosion was realised also by surface coating with Zn metal. (C) 2002 Elsevier Science B.V. All rights reserved.