Towards the diffusion source cost reduction for NdFeB grain boundary diffusion process

doi:10.1016/j.jmst.2019.08.009

Abstract

Abstract:

Aiming at improving the performance/cost ratio in grain boundary diffusion process (GBDP), the critical RE containing Pr-Al-Cu alloy, less expensive RE containing La-Al-Cu alloy and non-RE Al-Cu alloy were employed as the diffusion sources. The preliminary results show that the coercivity was successfully enhanced from 1000 kA/m to 1695, 1156 and 1125 kA/m by Pr₇₀Al₂₀Cu₁₀, La₇₀Al₂₀Cu₁₀ and Al₇₅Cu₂₅ (at.%) alloys diffusion, respectively, due to the formation of (Nd,Pr)-Fe-B, La₂O₃ and c-Nd₂O₃ phases respectively, after diffusion. It is also found that the corrosion resistance can be improved by Al-Cu diffusion due to the positive effects of Al and Cu elements in grain boundary. The present results demonstrated the various coercivity enhancement mechanisms for the GBDP based on different diffusion sources, and provided feasible solutions for cost reduction of GBDP and NdFeB production by saving RE resource.

Key words: Grain boundary diffusion, Cost reduction, Coercivity, Microstructure, Corrosion resistance

H.X. Zeng, Z.W. Liu, J.S. Zhang, X.F. Liao, H.Y. Yu. Towards the diffusion source cost reduction for NdFeB grain boundary diffusion process[J]. J. Mater. Sci. Technol., 2020, 36: 50-54.

Figures/Tables 4

Fig. 1. Demagnetization curves of the original magnet and Pr-Al-Cu, La-Al-Cu and Al-Cu diffused magnets.

Fig. 2. Microstructures at D = 50 and 500 μm of the magnets diffused by Pr-Al-Cu (a1, a2), La-Al-Cu (b1, b2) and Al-Cu (c1, c2) alloys, the corresponding EDS mapping results at D = 50 μm are illustrated.

Fig. 3. BF field and HR images of the magnets diffused by La-Al-Cu (a, b) and Al-Cu (c, d) alloys, and the corresponding patterns of SAED and FFT.

Fig. 4. Polarization curves of the original magnet and Pr-Al-Cu, La-Al-Cu and Al-Cu diffused magnets (a) and their microstructures after corrosion (b-e). The corrosion current (i) and potential (E) are listed.

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