@article{Yao2024, 
author = {Bo Yao and Nan Kang and Xiangyu Li and Dou Li and Mohamed EL Mansori and Jing Chen and Haiou Yang and Hua Tan and Xin Lin},
title = {Toward understanding the microstructure characteristics, phase selection and magnetic properties of laser additive manufactured Nd-Fe-B permanent magnets},
year = {2024},
journal = {International Journal of Extreme Manufacturing},
volume = {6},
number = {1},
pages = {015002},
keywords = {laser additive manufacturing (LAM), Nd-Fe-B permanent magnets, numerical simulation, microstructure, magnetic properties},
url = {https://www.sciopen.com/article/10.1088/2631-7990/ad0472},
doi = {10.1088/2631-7990/ad0472},
abstract = {Nd-Fe-B permanent magnets play a crucial role in energy conversion and electronic devices. The essential magnetic properties of Nd-Fe-B magnets, particularly coercivity and remanent magnetization, are significantly influenced by the phase characteristics and microstructure. In this work, Nd-Fe-B magnets were manufactured using vacuum induction melting (VIM), laser directed energy deposition (LDED) and laser powder bed fusion (LPBF) technologies. The microstructure evolution and phase selection of Nd-Fe-B magnets were then clarified in detail. The results indicated that the solidification velocity (V) and cooling rate (R) are key factors in the phase selection. In terms of the VIM-casting Nd-Fe-B magnet, a large volume fraction of the α-Fe soft magnetic phase (39.7 vol.%) and Nd2Fe17Bx metastable phase (34.7 vol.%) are formed due to the low R (2.3 × 10−1 ℃ s−1), whereas only a minor fraction of the Nd2Fe14B hard magnetic phase (5.15 vol.%) is presented. For the LDED-processed Nd-Fe-B deposit, although the Nd2Fe14B hard magnetic phase also had a low value (3.4 vol.%) as the values of V (<10−2 m s−1) and R (5.06 × 103 ℃ s−1) increased, part of the α-Fe soft magnetic phase (31.7 vol.%) is suppressed, and a higher volume of Nd2Fe17Bx metastable phases (47.5 vol.%) are formed. As a result, both the VIM-casting and LDED-processed Nd-Fe-B deposits exhibited poor magnetic properties. In contrast, employing the high values of V (>10−2 m s−1) and R (1.45 × 106 ℃ s−1) in the LPBF process resulted in the substantial formation of the Nd2Fe14B hard magnetic phase (55.8 vol.%) directly from the liquid, while the α-Fe soft magnetic phase and Nd2Fe17Bx metastable phase precipitation are suppressed in the LPBF-processed Nd-Fe-B magnet. Additionally, crystallographic texture analysis reveals that the LPBF-processed Nd-Fe-B magnets exhibit isotropic magnetic characteristics. Consequently, the LPBF-processed Nd-Fe-B deposit, exhibiting a coercivity of 656 kA m−1, remanence of 0.79 T and maximum energy product of 71.5 kJ m−3, achieved an acceptable magnetic performance, comparable to other additive manufacturing processed Nd-Fe-B magnets from MQP (Nd-lean) Nd-Fe-B powder.}
}