Improved temperature and corrosion behaviour of nanocomposite Nd2(Fe,Co,M)14B/α-Fe magnets

The characteristics of the magnetic properties nanocomposite Nd-2(Fe,Co,M)(14)B/alpha-Fe magnets obtained by high energy ball milling and powder metallurgy routes have been improved by appropriate Al-Cr, Cr, Zr additions. Using a single phase close to the stoichiometric composition, nanocomposite Nd-12.6(Fe,Co,M)(81.4)B-6/alpha-Fe magnets with better temperature stability are produced, due to the disappearance of the Nd-rich grain boundary phase in Nd-2(Fe,Co)(14)B/alpha-Fe materials, If the content of the soft magnetic alpha-Fe phase in Nd-2(Fe,Co,M)(14)B/alpha-Fe composities increases, the thermal stability of the coercivity increases, too. For a Nd12.6Fe69.3Co11.6Zr0.5B6/alpha-Fe magnet, containing 37.5 vol% alpha-Fe, the temperature coefficients (from 293 to 413 K) of remanence alpha(J(r)) and coercivity beta(H-j(c)) are: = 0.07 and - 0.35% K-1, respectively. Nanocomposite magnets appears to he more corrosion resistant than sintered Nd-Fe-B magnets. (C) 2000 Elsevier Science S.A. All rights reserved.