Effects of (Nd,Pr)Hx intergranular addition on the mechanical properties of Nd-Pr-Ce-Fe-B sintered magnets

Abstract

Influences of (Nd, Pr)H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> 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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> incorporation. The (Nd, Pr)H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> 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 RE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">14</sub> B matrix phase grains. Besides, the hydrogen desorption behavior also demonstrates that the excessive hydrogen introduced by (Nd, Pr)H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> 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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> incorporation satisfies the constraints of cost, magnetic, and mechanical properties simultaneously, thereby possessing competitive advantages for mass production.