OPTIMIZING THE MICROSTRUCTURE OF LOW-REM ND-FE-B SINTERED MAGNET USING TB3CO0.6CU0.4HX ADDITION

1 SKOTNICOVÁ Kateřina
Co-authors:
2 BURKHANOV Gennady S. 1 ČEGAN Tomáš 2 KOLCHUGINA Natalia B. 3 LUKIN Alexander A. 1 ŽIVOTSKÝ Ondřej 2 PROKOFEV Pavel A. 1 KURSA Miroslav
Institutions:
1 VSB-Technical University of Ostrava, Regional materials science and technology centre, Ostrava, Czech Republic, EU, katerina.skotnicova@vsb.cz
2 Baikov Institute of Metallurgy and Materials Science, Russian Academy of Sciences, Moscow, Russian Federation
3 JSC SPETSMAGNIT”, Moscow, Russian Federation
Conference:
27th International Conference on Metallurgy and Materials, Hotel Voronez I, Brno, Czech Republic, EU, May 23rd - 25th 2018
Proceedings:
Proceedings 27th International Conference on Metallurgy and Materials
Pages:
1710-1715
ISBN:
978-80-87294-84-0
ISSN:
2694-9296
Published:
24th October 2018
Proceedings of the conference were published in Web of Science and Scopus.
Metrics:
18 views / 3 downloads
Abstract

Nd-Fe-B permanent magnets are key materials in the electric power system and they are indispensable for the future success of environmentally beneficial technologies. The hysteretic characteristics of sintered Nd-Fe-B magnets are highly sensitive to their microstructure and composition of phases. This paper is focused on the coercivity enhancement of the near-stoichiometric Nd2Fe14B-based magnet by optimizing microstructure, which included processes of grain boundary diffusion and grain boundary structuring via the application of hydrogenated Tb3Co0.6Cu0.4Hx compound added to the powder mixture. The base alloy having the composition Nd-24.0, Pr-6.5, Dy-0.5, B-1.0, Al-0.2, Fe-balance was prepared by strip-casting technique and subjected to hydrogen decrepitation during heating to 270 °C in a hydrogen flow at a pressure of 0.1 MPa and subsequent 1 h dwell at this temperature. The Tb3Co0.6Cu0.4 alloy was prepared by arc melting of starting components in an argon atmosphere on a water-cooled copper bottom using a non-consumable tungsten electrode. The ingot was subjected to homogenizing annealing at 600 °C for 90 h and subsequent hydrogenation under the conditions used for the decrepitation of the strip-cast alloy. Hydrogenated Tb3Co0.6Cu0.4Hx compound and hydrogen-decrepitated strip-cast alloy were mixed and subjected to mechanical activation. The microstructure, phase composition and distributions of REM, Co, Cu for the prepared magnets were investigated by SEM/EDX method. It was found that the total REM content in the main magnetic (Nd, Pr, Tb)2Fe14B phase was ~ 30 wt.%. Intergranular Nd-rich phases differing by their Tb, Co, Cu contents were identified. Studies of the stability of structure-sensitive parameter, namely, the coercive force jHc of the sintered magnet prepared with 2 wt.% of Tb3Co0.6Cu0.4Hx addition to the low-temperature heat treatments show the increase in the coercive force up to 1480 kA/m. This phenomenon is not typical of sintered Nd-Fe-B magnets, which usually demonstrates the drop (or invariance) of the coercive force after low-temperature heat treatments at 350-450 °C.

Keywords: Nd-Fe-B magnets, strip casting, hydrides, heat treatment, coercivity.
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