Lean neodymium Nd–Fe–B magnets containing minor addition of titanium

Abstract

The effect of titanium addition on the structure and magnetic properties was studied for the nanocomposite Nd 7 Fe 79-x B 14 Ti x and Nd 8 Fe 78-x B 14 Ti x systems. The alloys were rapidly solidified by melt-spinning with the roll speed 20 m/s. The overquenched, amorphous ribbons were subsequently crystallization annealed for 20 min at 953-973 K. It was found that the addition of 2 and 4 at% of Ti leads to a substantial increase of the coercivity and maximum energy product of the nanocomposite magnets while maintaining the remanence unchanged. The highest properties were obtained for the alloys containing 4 at% of Ti. The maximum energy product of 143 kJ/ m 3 was achieved for the Nd 8 Fe 74 B 14 Ti 4 alloy. The TEM studies showed substantial differences in the morphology of the alloys. The ternary alloys contain grains of various sizes of approximately 300 nm. The alloys containing 4 at% of Ti exhibit more homogeneous structure with the crystal sizes up to 30 and 50 nm for the Nd 8 Fe 74 B 14 Ti 4 and Nd 7 Fe 75 B 14 Ti 4 alloys, respectively. More detailed information on the phase constitution was obtained from the Mössbauer spectroscopy. Comparison of the Ti-free and 4 at% Ti alloys revealed that the amount of the hard magnetic Nd 2 Fe 14 B phase decreases from 84.53 to 69.88% for the Nd 7 Fe 79-x B 14 Ti x system and increased from 66.60 to 82.48% for Nd 8 Fe 78-x B 14 Ti x system.

Ti‐Doped Nanocomposite Pr2Fe14B/α‐Fe Ribbons with High Coercivity

“…The addition of 4 at% Ti in Nd 8 Fe 78 B 14 could produce a coercivity value of 648 kA m À1 . [17] Based on the above discussion, the coercivity value reported previously is not more than 850 kA m À1 in Ti-doped nanocomposite ribbons. It is worthy to further improve the coercivity value which can be perfectly used for the nanocomposite bonded magnet.…”

“…The addition of 4 at% Ti in could produce a coercivity value of 648 kA m −1 . [ 17 ]…”

Effect of Composition and Structure on the Properties of Ti Containing Nd-Fe-B Rapidly Quenched Alloys

“…The rather high boron content is to improve the amorphisation ability and titanium is added for coercivity increase. Our earlier studies showed that the 4 at.% of Ti is an optimal concentration for low Nd alloys [8], [9]. It is apparent from the data shown in Table I that the addition of titanium results in a substantial increase of the coercivity, when compared with the ternary alloy.…”

Fe precipitation at the grain boundaries in Zn‐reacted Nd–Fe–B magnets: Experimental and first‐principles studies

“…Due to the multiple domains structure and magnetic exchange coupling, the actual coercivity value of such magnets (15 kOe) is far below the magnetic anisotropy field of the NdFeB phase (72 kOe) (). Several recent experimental studies have revealed that the local structures around the grain boundaries (GBs) of sintered Nd–Fe–B magnets significantly affect their coercivity . For effective prevention of the exchange coupling between the grains, the GBs must be non‐ferromagnetic to work as a magnetic isolation interface and to block magnetic domain movement.…”