The effects of the hydrogenation-disproportionation-desorption-recombination (HDDR) process on the structure and the magnetic properties of the mechanical alloying (MA) prepared Nd8Fe84 Ti8 alloy and its nitride count...The effects of the hydrogenation-disproportionation-desorption-recombination (HDDR) process on the structure and the magnetic properties of the mechanical alloying (MA) prepared Nd8Fe84 Ti8 alloy and its nitride counterpart have been studied in detail. It has been found that Nd(Fe, Ti)12Hδ is formed in the temperature range from 300 to 550°℃. The disproportionation is ready to start at 550°℃ and is complete at 960°℃.The desorption and the recombination are almost synchronized. The phase of Nd(Fe,Ti)7 is formed at 750°℃ during the HDDR treatment. With increasing temperature of HDDR process, the metastable structure of TbCu7 type is gradually transformed into the structure of ThMn12 type. The intrinsic coercivity and the maximum magnetic energy product increase with increasing temperature of HDDR process.展开更多
This review summarizes the recent advances on the application of ^(57)Fe Mössbauer spectrometry to study the magnetic and phase characteristics of Nd–Fe–B-based permanent magnets. First of all, the hyperfine st...This review summarizes the recent advances on the application of ^(57)Fe Mössbauer spectrometry to study the magnetic and phase characteristics of Nd–Fe–B-based permanent magnets. First of all, the hyperfine structures of the Ce_(2)Fe_(14)B,(Ce,Nd)_(2)Fe_(14)B and MM_(2)Fe_(14)B phases are well-defined by using the model based on the Wigner-Seitz analysis of the crystal structure. The results show that the isomer shift δ and the quadrupole splitting öEQ of those 2:14:1 phases show minor changes with the Nd content, while the hyperfine field Bhfincreases monotonically with increasing Nd content and its value is influenced by the element segregation and phase separation in the 2:14:1 phase. Then, the hyperfine structures of the low fraction secondary phases are determined by the ^(57)Fe Mössbauer spectrometry due to its high sensitivity. On this basis,the content, magnetic behavior, and magnetization of the REFe_(2) phase, the amorphous grain boundary(GB) phase, and the amorphous worm-like phase, as well as their effects on the magnetic properties, are systematically studied.展开更多
In traditional Nd-Fe-B-based sintered magnets,the composition,role of each element and microstruc-tures have been extensively investigated globally since they were invented in 1983.However,the effects of boron(B)conte...In traditional Nd-Fe-B-based sintered magnets,the composition,role of each element and microstruc-tures have been extensively investigated globally since they were invented in 1983.However,the effects of boron(B)content and post-sinter annealing(PSA)on the microstructure and magnetic properties have been least studied so far and the relative mechanisms are not yet clear.In this paper,we investigated the influence of B on the magnetic performance and microstructure of Nd-Fe-B sintered magnets origi-nally containing copper(Cu),gallium(Ga)and titanium(Ti).It is shown that the intrinsic coercivity has a substantial increment of 2.86 kOe and the remanence has a slight reduction of 0.16 kGs when B content is reduced from 0.980 wt.%to 0.900 wt.%.Moreover,there is a coercivity increment of 27.3%and 65.3%for samples with 0.980 wt.%and 0.900 wt.%B content after PSA,respectively.It is shown that the im-pacts of B content and PSA are significant and their regulation mechanisms are worthwhile to be studied systematically.Furthermore,it is revealed by microstructural analysis that high coercivity of the sample with 0.900 wt.%B after PSA results from the uniform distribution of Ga,Cu,Nd,and the formation of RE 6(Fe,M)14(RE=Pr,Nd,M=Cu,Ga)compound in triple junction phases.The dilution of Fe content in grain boundary phases(GB phases)also plays an important role.It is found out that decrease of the re-manence is mainly due to reduction of the matrix phase and c-axis alignment degree.In this study,we explored a new path to develop Nd-Fe-B-based sintered magnets with high comprehensive properties by novel approaches through varying B content,PSA technique and co-adding trace elements.展开更多
文摘The effects of the hydrogenation-disproportionation-desorption-recombination (HDDR) process on the structure and the magnetic properties of the mechanical alloying (MA) prepared Nd8Fe84 Ti8 alloy and its nitride counterpart have been studied in detail. It has been found that Nd(Fe, Ti)12Hδ is formed in the temperature range from 300 to 550°℃. The disproportionation is ready to start at 550°℃ and is complete at 960°℃.The desorption and the recombination are almost synchronized. The phase of Nd(Fe,Ti)7 is formed at 750°℃ during the HDDR treatment. With increasing temperature of HDDR process, the metastable structure of TbCu7 type is gradually transformed into the structure of ThMn12 type. The intrinsic coercivity and the maximum magnetic energy product increase with increasing temperature of HDDR process.
基金Project supported by the Zhejiang Provincial Natural Science Foundation of China(Grant Nos.LY20E010002,LR18E010001,and LD19E010001)the National Natural Science Foundation of China(Grant Nos.U1704253 and 51801047)+2 种基金Liaoning Revitalization Talents Program(Grant No.XLYC1807177)the Key Research and Development plan of Zhejiang Province,China(Grant No.2020C05014)Ten Thousand Talents Plan of Zhejiang Province,China(Grant No.2018R52003)。
文摘This review summarizes the recent advances on the application of ^(57)Fe Mössbauer spectrometry to study the magnetic and phase characteristics of Nd–Fe–B-based permanent magnets. First of all, the hyperfine structures of the Ce_(2)Fe_(14)B,(Ce,Nd)_(2)Fe_(14)B and MM_(2)Fe_(14)B phases are well-defined by using the model based on the Wigner-Seitz analysis of the crystal structure. The results show that the isomer shift δ and the quadrupole splitting öEQ of those 2:14:1 phases show minor changes with the Nd content, while the hyperfine field Bhfincreases monotonically with increasing Nd content and its value is influenced by the element segregation and phase separation in the 2:14:1 phase. Then, the hyperfine structures of the low fraction secondary phases are determined by the ^(57)Fe Mössbauer spectrometry due to its high sensitivity. On this basis,the content, magnetic behavior, and magnetization of the REFe_(2) phase, the amorphous grain boundary(GB) phase, and the amorphous worm-like phase, as well as their effects on the magnetic properties, are systematically studied.
基金supported by the National Natural Science Foundation of China(Nos.52371188,52061015)Young Talents Program of Jiangxi Provincial Major Discipline Academic and Technical Leaders Training Program(No.20212BCJ23008)+5 种基金Jiangxi Provincial Natural Science Foundation(No.20212BAB214018)the Program of Qingjiang Excellent Young Talents of Jiangxi University of Science and Technology(No.JXUSTQJYX2020003)National College Students Innovation and Entrepreneurship Training Program(No.202110407013)Technology Program of Fujian Province(Nos.2020H6027,2021T3063)Self-deployed Projects of Ganjiang Innovation Academy,Chinese Academy of Sciences(No.E055B002)the Key Research Program of the Chinese Academy of Sciences(No.ZDRW-CN-2021–3).
文摘In traditional Nd-Fe-B-based sintered magnets,the composition,role of each element and microstruc-tures have been extensively investigated globally since they were invented in 1983.However,the effects of boron(B)content and post-sinter annealing(PSA)on the microstructure and magnetic properties have been least studied so far and the relative mechanisms are not yet clear.In this paper,we investigated the influence of B on the magnetic performance and microstructure of Nd-Fe-B sintered magnets origi-nally containing copper(Cu),gallium(Ga)and titanium(Ti).It is shown that the intrinsic coercivity has a substantial increment of 2.86 kOe and the remanence has a slight reduction of 0.16 kGs when B content is reduced from 0.980 wt.%to 0.900 wt.%.Moreover,there is a coercivity increment of 27.3%and 65.3%for samples with 0.980 wt.%and 0.900 wt.%B content after PSA,respectively.It is shown that the im-pacts of B content and PSA are significant and their regulation mechanisms are worthwhile to be studied systematically.Furthermore,it is revealed by microstructural analysis that high coercivity of the sample with 0.900 wt.%B after PSA results from the uniform distribution of Ga,Cu,Nd,and the formation of RE 6(Fe,M)14(RE=Pr,Nd,M=Cu,Ga)compound in triple junction phases.The dilution of Fe content in grain boundary phases(GB phases)also plays an important role.It is found out that decrease of the re-manence is mainly due to reduction of the matrix phase and c-axis alignment degree.In this study,we explored a new path to develop Nd-Fe-B-based sintered magnets with high comprehensive properties by novel approaches through varying B content,PSA technique and co-adding trace elements.
