# Fileset

[REPM2025_O14-4_Ishii.pdf](https://mdr.nims.go.jp/filesets/56bc8160-d946-45d5-8e02-7b88f4ac0c21/download)

## Creator

Akimitsu Ishii, Toshiyuki Koyama, Taichi Abe, Machiko Ode

## Rights

[Creative Commons BY Attribution 4.0 International](https://creativecommons.org/licenses/by/4.0/)

## Other metadata

[Phase-field simulation of liquid-phase sintering coupled with a CALPHAD database of Nd-Fe-B-Cu system](https://mdr.nims.go.jp/datasets/87dc32e6-5c4e-4657-bd14-7490975d27ac)

## Fulltext

REPM2025Phase-field simulation of liquid-phase sintering coupled with a CALPHAD database of Nd-Fe-B-Cu systemThu. July 31Theory & Simulations[O14-4] 11:40 – 11:55Akimitsu Ishii1, Toshiyuki Koyama1, Taichi Abe1, Machiko Ode11 National Institute for Materials ScienceBackground1EV・HEV*Motor**Nd-Fe-B magnetsMagnetizationMagnetization CurveMagnetic fieldCoercivity*https://www.webcg.net/articles/-/38278**https://motor-fan.jp/tech/article/35211T.T. Sasaki et al., Acta Mater. 115 (2016) 269–277.MicrostructureHeating Temp. [°C]Time [s]900-1100°C~ 600°CNd-Fe-B-...PackingLiquid-phasesinteringAnnealingProcessingSurface treatment…Nd-rich phases meltBackground2*https://www.webcg.net/articles/-/38278**https://motor-fan.jp/tech/article/35211Heating Temp. [°C]Time [s]900-1100°C~ 600°CT.T. Sasaki et al., Acta Mater. 115 (2016) 269–277.MicrostructureNd-Fe-B-...PackingLiquid-phasesinteringAnnealingProcessingSurface treatment…Nd-rich phases meltKey factors enhancing the coercivity:✓ High density✓ Small crystal grains of Nd2Fe14B (T1) phase✓ High volume fraction of the T1 phase✓ Thin grain boundary phases uniformly cover the T1 phasesT.T. Sasaki et al., Acta Mater. 115 (2016) 269–277.MicrostructureT. Koyama, T. Abe, et al., STAM, 22 (2021).Phase-field Model of Liquid-phase Sintering3W. Villanueva et al., Comput. Mater. Sci. 47 (2009) 512–520.Ravas modelH. Ravash et al., J. Eur. Ceram. Soc. 37 (2017) 2265–2275.Villanueva modelA. Ishii et al., Mater. Today Commun. 40 (2024) 110116.New phase-field model of liquid-phase sinteringDensificationNOT considering rigid-body motionRigid-body motionParticle1 mGasLiq.SolidGB[-]LPS simulation for model validation using hypothetical ternary system.DensityTimeInitial stageIntermediate stageFinal stageGreen body densityMicrostructural Evolution (Hypothetical material)4Initial state DensificationRearrangementPenetration1 mGasLiq. Solid GBPoreApplication to Nd-Fe-B magnets51 mSimulation conditions• Nd-Fe-B-Cu quaternary system• Thermodynamic (CALPHAD) database[T. Abe et al., STAM 22 (2021) 557–570.]• Initial composition: Fe-6.0B-15.0Nd-0.1Cu (at%)• Temperature: 1000°C• Diffusivity ratios:Solid : GB : Liquid = 1 : 10 : 100• Interfacial energy ratios:solid-pore = 1.92 J/m2[Y. Ainai et al., Appl. Phys. Exp. 13 (2020) 045502.]solid-solid = 0.77 J/m2, solid-liquid = 0.47 J/m2liquid-pore = 1.54 J/m2VacuumLiq. T1 GBResults (Nd-Fe-B-Cu system)61 mLiq. T1 GB Vacuum0.77cNd0.000.82cFe0.000.10cB0.000.01cCu0.00Initial liquid phase distributions (Nd-Fe-B-Cu system)71 mVacuumLiq. T1 GB• Only the initial liquid phase distribution was changed.• T1 phase distribution, liquid phase volume, and compositions were not changed.Simulation results (Nd-Fe-B-Cu system)8VacuumLiq. T1 GB1 mComparison (Nd-Fe-B-Cu system)9Liq. T1 GB VacuumDensity [%]StepsMean radius [nm]Steps40 nm29.8 nm 56.1 nm Radius of the initial liquid phasesEffect of sintering temperature101 m1000°C VacuumLiq. T1 GBTemperature dependence of phase fractions obtained from CALPHAD calculation900°C 1100°C Phase fractionTemperature [°C]Comparison of Nd concentration distribution111000°C Temperature dependence of liquid composition obtained from CALPHAD calculation900°C 1100°C Composition of liquid1 m0.60Molar fraction of Nd0.00Temperature [°C]Additional simulation of solidification121 mVacuumLiq. T1 GB900 °C ⇒ 600 °C 1100 °C ⇒ 600 °C 1000 °C ⇒ 600 °C • We developed a new framework to simulate microstructural evolution of Nd-Fe-B sintered magnets during liquid-phase sintering. • A new phase-field model of liquid-phase sintering was developed and coupled with an Nd-Fe-B-Cu thermodynamic database.• The simulation results demonstrate that our framework has the potential to provide useful insights for the development of the Nd magnets.13ConclusionThis research was supported by the Materials Open Platform for Permanent Magnet at NIMSAcknowledgement• Model details ⇒ A. Ishii et al., Meter. Today Commun. 40 (2024), 110116.• Further Discussions ⇒ A. Ishii et al., J. Alloy. Compd., 1025 (2025) 180266.Related papers 既定のセクション スライド 0: Phase-field simulation of liquid-phase sintering coupled with a CALPHAD database of  Nd-Fe-B-Cu system スライド 1: Background スライド 2: Background スライド 3: Phase-field Model of Liquid-phase Sintering スライド 4: Microstructural Evolution (Hypothetical material) スライド 5: Application to Nd-Fe-B magnets スライド 6: Results (Nd-Fe-B-Cu system) スライド 7: Initial liquid phase distributions (Nd-Fe-B-Cu system) スライド 8: Simulation results (Nd-Fe-B-Cu system) スライド 9: Comparison (Nd-Fe-B-Cu system) スライド 10: Effect of sintering temperature スライド 11: Comparison of Nd concentration distribution スライド 12: Additional simulation of solidification スライド 13: Conclusion