Chapter 1 Introduction 1
1.1 Rare EarthPermanent-magnetAlloys 2
1.1.1 Rare earth 2
1.1.2 Classification and development of rare earth permanent-magnet alloys 2
1.1.3 Crystal structure of rare earth permanent-magnet alloys 4
1.1.4 Magnetic parameters of rare earth permanent-magnet alloys 7
1.1.5 Criterion of permanent-magnet alloys(materials) 8
1.2 Principle for Alloy Phase and Phase Transformation and Growth Rule of New Phase 8
1.2.1 Phase 9
1.2.2 Phase transformation 9
1.2.3 Alloy 9
1.2.4 Material 10
1.2.5 Alloy phase 10
1.2.6 Solid solution 10
1.2.7 Exsolution precipitation 10
1.2.8 Thermodynamic bases for phase transformation and classification 10
1.2.9 Single crystal 17
1.2.10 Single crystal superalloy 17
1.2.11 Enthalpy 18
1.2.12 Entropy 18
1.2.13 Latent heat of phase transformation 19
1.2.14 Driving force of phase transformation 19
1.2.15 Rule of growing up of new phase 20
1.3 Research Methods of the Magnetic Properties of Rare Earth Permanent Magnets 21
Reterences 25
Chapter 2 The First Generation Rare Earth Permanent-magnet Alloys 27
2.1 High temperature Phase Transition and Magnetic Properties of SmCo5 Permanent-magnet Alloys 28
2.2 The in Situ and Dynamic Observation on High Temperature Phase Transformation of SmCo5 Permanent Magnetic Alloyat 25-750℃ 35
2.2.1 Magnetic measurement 36
2.2.2 Sample preparation and experiment method 38
2.2.3 Influence of annealing treated specimen on coercivity 39
2.2.4 The in situ and dynamic observation by 1000kV HVEM under heating condition 41
2.2.5 Discussion 50
2.3 Magnetism and the in Situ and Dynamic Observation of Permanent MagneticAlloy of SmCo5 byAnnealing at 600-1000℃ 54
2.3.1 Specimen preparation and experimental method 55
2.3.2 Analysis on chemical composition of the SmCo5 permanent magnetic alloy 55
2.3.3 Magnetic measurement 55
2.3.4 Structure of magnetic domain 56
2.3.5 Irreversible loss of SmCo5 permanent magnetic alloy after annealing at 25-1000℃ 57
2.3.6 Electronic energy spectrum experiment and analysis of SmCos permanent magnetic alloy 58
2.3.7 The in situ and dynamic observation on eutectoid decomposition of SmCo5 by electronic microscope 61
2.3.8 The in situ and dynamic observation of SmCo5 in thermal state using transmission electronic microscope 62
2.3.9 The in situ and dynamic observation on SmCo5 in thermal condition of 750-960℃ by Transmission Electronic Microscope 63
2.3.10 Discussion 65
2.3.11 Conclusions 67
2.4 Analysis on Variation ofthe Coercivity and Phase Transformation 68
2.4.1 Specimen preparation and experimental method 68
2.4.2 Experimental result and discussion 69
2.4.3 Conclusions 74
2.5 The Optic-electronic Spectrum Study on SmCo5 Permanent MagneticAlloy 74
2.5.1 Specimen preparation technique and experimental condition of optic-electronic energy spectrum 75
2.5.2 Investigation on surface composition of SmCo5 75
2.5.3 Atoms concentration variation of elements of samarium,cobalt and oxygen from surface to depth 76
2.5.4 Surface compound 77
2.5.5 Conclusions 77
2.6 Analysis on Magnetic Hysteresis Loop of SmCo5 Permanent MagneticAlloy 77
2.6.1 Specimen preparation technique,magnetic measurement and transmission microscope condition and experimental method 78
2.6.2 Analysis on chemical composition of three kinds of specimens 78
2.6.3 Analysis on preparation technique 80
2.6 4 Curve of magnetic performance and analysis at 77-550K 80
2.6.5 Observation and analysis on specimen using TEM 81
2.6.6 Conclusions 82
2.7 Magnetism of SmCo5 Permanent Alloy at 1.5-523K 82
2.7.1 Specimen preparation technique,magnetic measurement apparatus and experimental method 82
2.7.2 Magnetism measurement and curve of SmCo5 permanent magnetic alloy at 1.5K and 40K 83
2.7.3 Measurement of demagnetization curve and value of magnetic parameter at-196-250℃ by magnetic parameter measurement apparatus 85
2.7.4 Reversible temperature coefficient of SmCo5 at-196-250℃ 87
2.7.5 Coercivity of SmCo5 at 475-1000℃ 87
2.7.6 Discussion 89
2.7.7 Conclusions 90
References 90
Chapter 3 The Second Generation Rare Earth Permanent-magnet Alloys 95
3.1 Phase Precipitation,Phase Transformation at High Temperature and Magnetism of High Coercivity Sm(Co,Cu,Fe,Zr)7.4 96
3.1.1 Specimen preparation process and experimental method 97
3.1.2 Results of specimen magnetic measurement 98
3.1.3 Microtexture of the alloy at room temperature 99
3.1.4 The in situ and dynamic observation on precipitation,growth up and high temperature phase transformation of cellular structure from room temperature to high temperature 101
3.1.5 Conclusions 116
3.2 Function of Zirconium on Sm(Co,Cu,Fe,Zr)7.4 Permanent Magnetic Alloy＆Observation and Analysis by Electron Microscope 118
3.2.1 Specimen preparation and experimental method 118
3.2.2 Research on function of Zirconium 118
3.2.3 Conclusions 121
3.3 Magnetism of High Coercivity Sm(Co,Cu,Fe,M)7 4Permanent Magnetic Alloy at 1.5-523K 121
3.3.1 Preparation of specimen and magnetism measurement apparatusz and measurement method 122
3.3.2 Measurement results and discussion 122
3.3.3 Conclusions 125
References 126
Chapter 4 The Third Generation Rare Earth Permanent Magnet 129
4.1 Improvement of the Properties of NdFeB Permanent Magnets Due to Element Substitutions 129
4.2 Magnetic Properties and the Occupancy of Co and Ga Atoms for NdFe(Co,Al,Ga)B Permanent-Magnetic Alloys 133
4.2.1 Preparation and method 133
4.2.2 Nd16Fe77-xCoxB7 alloy 134
4.2.3 Nd16Co10Fe67-yAlyB7 and Nd16Co16Fe61-yAlyB7 alloys 136
4.2.4 Nd16Co16Fe61-xGaxB7 alloy 138
4.2.5 Conclusions 144
4.3 The Studies of Main Phase Nd2Fe14B and Nd2(Fe,Co)14B in NdFeB Permanent-magnet Alloys 145
4.3.1 The preparation of samples and experimental methods 145
4.3.2 SEM analysis 145
4.3.3 The formation of Nd2Fe14B 146
4.3.4 M？ssbauer spectra at room temperature 146
4.3.5 Composition analysis and the studies of M？ssbauer spectra for Nd2(Fe,Co)14B 147
4.3.6 In situ and dynamic observation of TEM on Nd2Fe14B and Nd2(Fe,Co)14B 147
4.3.7 Conclusions 150
4.4 Studies on B-rich Phase in NdFeB Alloy 150
4.4.1 Preparation process and experimental method 151
4.4.2 The in situ and dynamic observation of Nd1.11Fe4B4 by TEM 151
4.4.3 Study on Nd1+εFe4B4 by X-Ray diffraction and M？ssbauer effect 153
4.4.4 Analysis on Nd1.1Fe4B4 phase 153
4.4.5 Relationship between B-rich phase and coercivity 155
4.4.6 Conclusions 156
4.5 Influence ofBoron Content in NdFeB on Nd2Fe14B Phase and Magnetic Property 156
4.5.1 Specimen preparation process and experimental method 157
4.5.2 Influence of boron content on alloy magnetic property and phase structure 157
4.5.3 Conclusions 161
4.6 High Curie Temperature NdFeCoGaB Permanent Magnetic Alloy 162
4.6.1 Preparation process and experiment method 162
4.6.2 Using cobalt to replace part of iron 163
4.6.3 Use Ga to replace part of iron in NdFeCoB alloy 163
4.6.4 Conclusions 168
4.7 Influence of Adding Element Dysprosium on Performance of NdFeB Alloy 168
4.7.1 Specimen preparation process and experimental method 169
4.7.2 Experiment result using SEM 169
4.7.3 Measurement of magnetism 170
4.7.4 Experiment result using transmission microscope 171
4.7.5 Distribution of Dy2O3 171
4.7.6 Conclusions 174
4.8 Nanocrystalline Microstructure and Coercivity Mechanism Model of NdFeB Alloys with Nb and Ga 174
4.8.1 Experimental procedure 175
4.8.2 Magnetic properties measuring 175
4.8.3 Study of M？ssbauer effect 176
4.8.4 Study of nano-microstructure of NdFeB alloys with Nb 178
4.8.5 Dynamic cross and microstructure of the NdFeB alloys with Nb and Dy 178
4.8.6 Dynamic cross and microstructure of the NdFeB alloys with Nb,Ga,Co and Dy 179
4.8.7 Curie temperature of the NdFeB alloys with Nb 180
4.8.8 New coercivity mechanism model of multi-component NdFeB alloys 182
4.8.9 Conclusions 183
4.9 In Situ and Dynamic Observation on Magnetic and Phase Transformation of Nd15Fe78B7 Permanent Magnet at High Temperature 184
4.9.1 Preparation process of specimen and experiment method 185
4.9.2 Microstructure and phase in crystal boundary of NdFeB permanent magnet 185
4.9.3 Phase transformation of microstructure of B-rich phase at high temperature 189
4.9.4 Phase transformation of microstructure of Nd-rich filmy belt in Nd15Fe78B7 crystal boundary at high temperature 190
4.9.5 Phase transformation of Nd2Fe14B base phase of Nd15Fe78B7 alloy at high temperature 193
4.9.6 Conclusions 194
4.10 In Situ and Dynamic Observation on High Temperature Phase Transformation and Magnetism of Nd16Fe77B7 Permanent Magnetic Alloy 195
4.10.1 Samples preparationprocess and experimental method 196
4.10.2 The in situ and dynamic observation on nanometer microstructure and high temperature phase transformation 196
4.10.3 Function of cobalt in NdFeCoB alloy 201
4.10.4 Magnetic characteristic measurement result and analysis 201
4.10.5 Curie temperature measurement result 202
4.10.6 Phase analysis by X-ray diffraction,lattice constant and cell volume 202
4.10.7 Relationship between aging temperature and coercivity of Nd16Fe69Co8B7 203
4.10.8 Conclusions 204
4.11 Analysis on Lamella Phase of Grain Boundary in Microstructure of NdFeB Permanent Magnetic Alloy 204
4.11.1 Experimental method 204
4.11.2 Magnetism measurement 205
4.11.3 Analysis on result of the in situ and dynamic observation of samples 205
4.12 Quick Quenched NdFeB Permanent Magnetic Alloy 215
4.12.1 Sample preparation technique and experimental method 215
4.12.2 Measurement result of quick quenched magnet 215
4.12.3 Relationship between crystallization temperature and coercivity 216
4.12.4 Microstructure at room temperature 216
4.12.5 The in situ and dynamic observation on the non-crystal sample transferring to micro-crystal by HVEM 216
4.12.6 Conclusions 217
4.13 Stability of the Rare Earth Permanent Magnetic Alloy 217
4.13.1 Stability on temperature 217
4.13.2 Time stability 224
4.13.3 Chemical stability 224
4.13.4 Conclusions 224
References 225
Chapter 5 Developments and Prospect of the Rare Earth Permanent-magnet Alloys 231
5.1 Overseas General Development 232
5.2 Domestic General Development 238
5.3 Development Survey of Preparation Technology 243
5.4 Application and Expectation 248
References 253
Appendix 257
Appendix 1 The Structure of Outer Electrons for Rare Earths 257
Appendix 2 Atomic and Ionic Radius of Rare Earths 258
Appendix 3 Physical Properties of Rare Earths 259
Appendix 4 Fundamental Physical Constants 261
Appendix 5 Conversion of magnetic quantity between SI and Gaussian units 262
Index 265