TY - JOUR
T1 - Microstructure and temperature dependent of coercivity of hot-deformed Nd-Fe-B magnets diffusion processed with Pr-Cu alloy
AU - Sepehri-Amin, H.
AU - Liu, Lihua
AU - Ohkubo, T.
AU - Yano, M.
AU - Shoji, T.
AU - Kato, A.
AU - Schrefl, T.
AU - Hono, K.
N1 - Funding Information:
This work was in part supported by CREST , JST and the future pioneering program “Development of magnetic material technology for high-efficiency motors” commissioned by the New Energy and Industrial Technology Development Organization (NEDO). L.H.L. acknowledges NIMS for the provision of the NIMS Junior Research Assistantship.
Publisher Copyright:
© 2015 Acta Materialia Inc. All rights reserved.
PY - 2015/10/15
Y1 - 2015/10/15
N2 - The coercivity of hot-deformed Nd-Fe-B magnet was substantially enhanced from 1.0 T to 2.6 T by the grain boundary diffusion process using Pr-Cu alloy. However, the temperature dependence of coercivity is larger compared to the sample diffusion processed with Nd-Cu. Microstructure studies showed a good isolation of platelet shaped Nd2Fe14B grains by Pr-rich intergranular phase, which explains pronounced coercivity at room temperature. Small portions of Nd2Fe14B become (Nd,Pr)2Fe14B phase, which has a higher anisotropy field compared to that of the Nd2Fe14B phase at room temperature, while it becomes lower than that of the Nd2Fe14B phase above ∼110 °C. Co is depleted from the (Nd,Pr)2Fe14B phase, which is considered to cause a slight decrease in Curie temperature. Micromagnetic simulations with the magnetically isolated grains including (Nd,Pr)2Fe14B regions showed that the degradation of thermal stability of coercivity in the Pr-Cu diffusion processed sample is due to the large temperature dependence of anisotropy field in the (Nd,Pr)2Fe14B regions.
AB - The coercivity of hot-deformed Nd-Fe-B magnet was substantially enhanced from 1.0 T to 2.6 T by the grain boundary diffusion process using Pr-Cu alloy. However, the temperature dependence of coercivity is larger compared to the sample diffusion processed with Nd-Cu. Microstructure studies showed a good isolation of platelet shaped Nd2Fe14B grains by Pr-rich intergranular phase, which explains pronounced coercivity at room temperature. Small portions of Nd2Fe14B become (Nd,Pr)2Fe14B phase, which has a higher anisotropy field compared to that of the Nd2Fe14B phase at room temperature, while it becomes lower than that of the Nd2Fe14B phase above ∼110 °C. Co is depleted from the (Nd,Pr)2Fe14B phase, which is considered to cause a slight decrease in Curie temperature. Micromagnetic simulations with the magnetically isolated grains including (Nd,Pr)2Fe14B regions showed that the degradation of thermal stability of coercivity in the Pr-Cu diffusion processed sample is due to the large temperature dependence of anisotropy field in the (Nd,Pr)2Fe14B regions.
KW - Coercivity
KW - Magnetic anisotropy field
KW - Microstructure
KW - Nd-Fe-B hot-deformed magnets
UR - http://www.scopus.com/inward/record.url?scp=84940372407&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84940372407&partnerID=8YFLogxK
U2 - 10.1016/j.actamat.2015.08.013
DO - 10.1016/j.actamat.2015.08.013
M3 - Article
AN - SCOPUS:84940372407
VL - 99
SP - 297
EP - 306
JO - Acta Materialia
JF - Acta Materialia
SN - 1359-6454
ER -