The influence of process parameters and alloy structure on the magnetic properties of NdDyFeBNb HD sintered magnets

Complete ductility in NdFeB-type alloys using the Hydrogen Ductilisation Process (HyDP)

“…There were some indications of alignment in the material, with an easy-axis in the z-direction (pressing direction); this direction can be seen again in Figure 6(a). In comparison, conventional sintered magnets with a similar composition to that used here have typically, a coercivity of 800-1000 kAm -1 and a remanence of 1200 mT [10,11].…”

“…To date the best magnetic properties have been for a Neomax-type alloy pressed at 5 t with a coercivity of 824 kAm -1 and a remanence of 770 mT. Although the coercivity is close to that expected for a M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 20 20 sintered magnet of a similar composition the remanence is significantly lower than that for a commercially produced sintered magnet based on the Neomax composition [10,11]. In order to achieve a significantly higher BH(max), the NdFe4B4 phase would have to be removed to reduce cracking, the cavitation would have to be eliminated and a higher level of deformation would have to be achieved.…”

A study of high-energy milling for the production of sintered PrFeB magnets

“…It is possible to identify at least seven steps: melting of the alloy, homogenization, milling, powder magnetic alignment and compaction, sintering and post-sintering heat treatment. Good HD sintered REFeB magnets have been produced using the "roller" ball milling (RBM) from alloys comminuted between 64.8 and 72.0 ks (18 and 20 hours, respectively) 2,3 . However, milling is time consuming, even using the hydrogen decrepitation (HD) process.…”

Estudo microestrutural e propriedades magnéticas em ímãs permanentes sinterizados a base de PrFeCoBNb com adições de elementos de ligas

“…Grossinger et al (1990), observaram uma queda significativa nos valores da coercividade em ímãs produzidos sem a utilização de terras raras pesadas como Tb e Dy, uma vez que a substituição do Nd ou Pr, por Tb ou Dy promove o aumento do campo de anisotropia (H a ) e conseqüentemente aumenta a coercividade ( i H c ). Takiishi et al (2004) reportaram bons valores para as propriedades magnéticas com ímãs processados com decrepitação de hidrogênio (HD) a partir de ligas com estequiometria Nd 14,5 Dy 1,5 Fe 76 B 7 Nb 1 e realçaram a influência do Dy na coercividade e sua relação com os tempos de moagem durante o processo. concentrações e constataram que o aumento das quantidades de Co adicionadas provocam um aumento da remanência e correspondente queda na coercividade explicada pela introdução de uma fase ferromagnética no contorno de grão, que reduz a isolação magnética entre os grãos.…”