Effects of (Nd, Pr)H<italic>x</italic> Intergranular Addition on the Mechanical Properties of Nd–Pr–Ce–Fe–B Sintered Magnets

Abstract

Influences of (Nd, Pr)H x additives on the microstructure and mechanical properties of Nd–Pr–Ce–Fe–B sintered magnets have been investigated. The results show that both the fracture toughness and bending strength exhibit a monotonically increasing trend with raised (Nd, Pr)H x incorporation. The (Nd, Pr)H x powders transform into metallic Nd/Pr with high reactivity upon dehydrogenation, increasing the volume fraction of rare earth-rich intergranular phase, and promoting the formation of thick and continuous grain boundary (GB) layer surrounding the RE2Fe14B matrix phase grains. Besides, the hydrogen desorption behavior also demonstrates that the excessive hydrogen introduced by (Nd, Pr)H x additives can be completely released upon high-temperature sintering. As a result, the crack propagation along the thick GBs is suppressed, giving rise to the substantially enhanced mechanical performance of bulk magnets. This paper suggests that the Nd–Pr–Ce–Fe–B permanent magnet with (Nd, Pr)H x incorporation satisfies the constraints of cost, magnetic, and mechanical properties simultaneously, thereby possessing competitive advantages for mass production.