Improved thermal stability of hard magnetic properties in rapidly solidified RE–TM–B alloys

Rapidly solidified nanocrystalline RE–TM–B (RE = Nd, Pr, Dy, TM = Fe, Co) alloys with enhanced hard magnetic properties were synthesized by melt spinning. The composition- and microstructure-dependent elevated temperature magnetic properties were investigated. The temperature coefficients of remanence (α) and coercivity (β) were determined. The effects of Pr substituting Nd, Co substituting Fe, Dy substituting RE, and grain size on the Curie temperature and thermal stability were studied. Co or Dy substitutions were found to have a significant beneficial effect on the thermal stability. Reducing grain size could also improve elevated temperature behavior. Maximum energy product (BH)max > 100 kJ/m3 could be obtained in compositionally optimized nanophase alloys at temperature of 473 K. Extremely low coefficients of α and β were realized in exchange coupled nanocomposite alloys. Bonded nanocomposite magnets with α = −0.052%/K and β = −0.0365%/K for 300–400 K were also successfully fabricated.