TY - JOUR
T1 - Diagram of constituent crystalline phases in a Nd–Fe–B–Cu sintered magnet by in-situ high-temperature synchrotron X-ray diffraction and its thermodynamic interpretation
AU - Kobayashi, Shintaro
AU - Abe, Taichi
AU - Martín-Cid, Andrés
AU - Kawaguchi, Shogo
AU - Suzuki, Motohiro
AU - Hirosawa, Satoshi
AU - Nakamura, Tetsuya
N1 - Funding Information:
We thank Dr. Nishiuchi and Dr. Fukagawa in Hitachi Metals, Ltd for providing samples. This study was conducted with the approval of the SPring-8 Program Advisory Committee (Proposal nos. 2019B1004, 2020A1299, 2020A1345, 2021A1019). This work was in part supported by ESICMM, Grant number JPMXP0112101004, through the Ministry of Education, Culture, Sports, Science and Technology (MEXT), and JSPS KAKENHI Grant number 20K15035.
Publisher Copyright:
© 2021 Elsevier B.V.
PY - 2022/2/5
Y1 - 2022/2/5
N2 - A crystalline phase diagram of a Nd–Fe–B–Cu sintered magnet up to 1100 °C was determined through in-situ synchrotron X-ray diffraction using a new sample mounting method that prevents high-temperature contact reactions between the sample and the quartz capillary tube container. Using this newly developed method, we successfully observed almost identical phase diagrams during heating and cooling, indicating thermodynamic equilibrium. In addition, we obtained changes in the constituent phase fraction after quenching. Temperature-reversible changes in the dhcp-Nd fraction were observed from 475 °C to 650 °C, corresponding to a eutectic reaction in the Nd–Cu phase. The fcc-NdOx fraction decreased with the increase in the Nd2O3 fraction above 1000 °C, which behavior was attributed to a phase change from fcc-NdOx to high-temperature liquid and hcp-Nd2O3 phases. The measurements verify the thermodynamic database recently constructed for CALPHAD calculations of the Nd–Fe–B–Cu–O system by assuming the local thermodynamic equilibrium of the Nd oxides within the microstructure of the magnet.
AB - A crystalline phase diagram of a Nd–Fe–B–Cu sintered magnet up to 1100 °C was determined through in-situ synchrotron X-ray diffraction using a new sample mounting method that prevents high-temperature contact reactions between the sample and the quartz capillary tube container. Using this newly developed method, we successfully observed almost identical phase diagrams during heating and cooling, indicating thermodynamic equilibrium. In addition, we obtained changes in the constituent phase fraction after quenching. Temperature-reversible changes in the dhcp-Nd fraction were observed from 475 °C to 650 °C, corresponding to a eutectic reaction in the Nd–Cu phase. The fcc-NdOx fraction decreased with the increase in the Nd2O3 fraction above 1000 °C, which behavior was attributed to a phase change from fcc-NdOx to high-temperature liquid and hcp-Nd2O3 phases. The measurements verify the thermodynamic database recently constructed for CALPHAD calculations of the Nd–Fe–B–Cu–O system by assuming the local thermodynamic equilibrium of the Nd oxides within the microstructure of the magnet.
KW - Permanent magnets
KW - Phase diagrams
KW - Synchrotron radiation
KW - Thermodynamic modeling
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U2 - 10.1016/j.jallcom.2021.162188
DO - 10.1016/j.jallcom.2021.162188
M3 - Article
AN - SCOPUS:85116900469
VL - 892
JO - Journal of Alloys and Compounds
JF - Journal of Alloys and Compounds
SN - 0925-8388
M1 - 162188
ER -