The distribution, morphologies and structures of intergranular Nd-rich phase in sintered Nd-Fe-B magnets were studied through electron microscopy. Backscattered electron （BSE） imaging revealed that Nd-rich particles...The distribution, morphologies and structures of intergranular Nd-rich phase in sintered Nd-Fe-B magnets were studied through electron microscopy. Backscattered electron （BSE） imaging revealed that Nd-rich particles with various morphologies and sizes were randomly distributed at the grain boundaries and the triple junctions of the tetragonal Nd2FelnB matrix. Through selected area electron diffraction （SAED） analysis under a systematic tilting condition, most intergranular Nd-rich phase particles, with sizes ranging from hundreds of nanometres to several micrometres, were identified as face-centred cubic （FCC） structure. Such particles possessed several approximate orientation relationships with their adjacent Nd2FelaB matrix grains, such as （002）Nd2Fe14B/ （200）FCC_Nd-rieh [120] Nd2Fe14B//[001]FCC Nd-fich, （002）Nd2Fe14B//（220）FCC_Nd-rich [110] Nd2Fe14B//[l12]FCC_Nd-rich, as well as （011）Nd2Fe14B// （13 1 ）rcc Nd-rich [111 ] Nd2Fe14B//[ 114]FCC Nd_rich, which could be attributed to minimising interracial energy. The combination of high- resolution electron microscopy with energy-dispersive X-ray spectroscopy revealed the internal inhomogeneous nature of Nd-rich phases. The large lattice distortion and nanoscale-ordered structures within a single Nd2rich grain were observed.展开更多
In this paper,dependence of magnetic properties on microstructure and composition of Ce-Fe-B sintered magnets with Cu-doped Ce-rich alloy addition was investigated.It shows that the maximum energy product(BH)(max)and ...In this paper,dependence of magnetic properties on microstructure and composition of Ce-Fe-B sintered magnets with Cu-doped Ce-rich alloy addition was investigated.It shows that the maximum energy product(BH)(max)and coercivity H(cj)of Ce-Fe-B sintered magnet are improved from 6.76 to 9.13 MGOe by 35.1%,and from 1.44 to 1.67 kOe by 16.0%,respectively,via adding 5 wt%liquid phase alloy of Ce(35.58)Fe(57.47)Cu6 B(0.95)(at%).Compared with the magnet without Cerich alloy addition,the volume fraction of the grain-boundary phase with low melting point increases in the magnet with Ce-rich alloy additio n,which is be ne ficial to imp roving the microstructure and promoting the coercivity enhancement of the magnet.In the Ce-Fe-B magnet with Ce-rich alloy addition,Cu and Ce enrich in the grain boundaries of the magnet after annealing,therefore the as-annealed magnet has a higher coercivity than the as-sintered magnet.A distinct Fe-rich layer with the average thickness of 60 nm is found in the grain boundaries in the magnet without Ce-rich alloy addition,but it seems that Fe-rich phase disappears in the magnet with Ce-rich alloy addition.The present work suggests that the further improvement of coercivity in the Ce-Fe-B sintered magnets is expectable by designing the composition and structure of added liquid phase alloys.展开更多
The ribbons of NdFeB/College of Material Science ＆ Engineering, Xihua University, Chengdu 610039, China-Fe composite alloy were prepared by melt spinning and post crystallizing technique. The element distri- butions ...The ribbons of NdFeB/College of Material Science ＆ Engineering, Xihua University, Chengdu 610039, China-Fe composite alloy were prepared by melt spinning and post crystallizing technique. The element distri- butions and phase component of both surfaces of as-spun ribbons were measured by energy dispersive spectrometry （EDS） and X-ray diffraction （XRD）. Because of the centrifugation, a segregation of B, Fe, and Nd concentrations was observed at the cross section. After crystallizing annealing, the element concentration segregation still existed in the as-crystallized ribbons. Due to the segregation of B, Fe, and Nd, the B-rich phase was observed near the wheel side surface. The B-rich phase may deteriorate the magnetic property of NdFeB/a-Fe composite alloy.展开更多
基金Foundation item： Project supported by the Chinese Ministry of Science and Technology （2012IM030500） and National Natural Science Foundation of China （51201015, 51271038, 51171048）
文摘The distribution, morphologies and structures of intergranular Nd-rich phase in sintered Nd-Fe-B magnets were studied through electron microscopy. Backscattered electron （BSE） imaging revealed that Nd-rich particles with various morphologies and sizes were randomly distributed at the grain boundaries and the triple junctions of the tetragonal Nd2FelnB matrix. Through selected area electron diffraction （SAED） analysis under a systematic tilting condition, most intergranular Nd-rich phase particles, with sizes ranging from hundreds of nanometres to several micrometres, were identified as face-centred cubic （FCC） structure. Such particles possessed several approximate orientation relationships with their adjacent Nd2FelaB matrix grains, such as （002）Nd2Fe14B/ （200）FCC_Nd-rieh [120] Nd2Fe14B//[001]FCC Nd-fich, （002）Nd2Fe14B//（220）FCC_Nd-rich [110] Nd2Fe14B//[l12]FCC_Nd-rich, as well as （011）Nd2Fe14B// （13 1 ）rcc Nd-rich [111 ] Nd2Fe14B//[ 114]FCC Nd_rich, which could be attributed to minimising interracial energy. The combination of high- resolution electron microscopy with energy-dispersive X-ray spectroscopy revealed the internal inhomogeneous nature of Nd-rich phases. The large lattice distortion and nanoscale-ordered structures within a single Nd2rich grain were observed.
基金Project supported by the National Natural Science Foundation of China(51590882)the Plan of National Key Research and Development of China(2016YFB0700903)
文摘In this paper,dependence of magnetic properties on microstructure and composition of Ce-Fe-B sintered magnets with Cu-doped Ce-rich alloy addition was investigated.It shows that the maximum energy product(BH)(max)and coercivity H(cj)of Ce-Fe-B sintered magnet are improved from 6.76 to 9.13 MGOe by 35.1%,and from 1.44 to 1.67 kOe by 16.0%,respectively,via adding 5 wt%liquid phase alloy of Ce(35.58)Fe(57.47)Cu6 B(0.95)(at%).Compared with the magnet without Cerich alloy addition,the volume fraction of the grain-boundary phase with low melting point increases in the magnet with Ce-rich alloy additio n,which is be ne ficial to imp roving the microstructure and promoting the coercivity enhancement of the magnet.In the Ce-Fe-B magnet with Ce-rich alloy addition,Cu and Ce enrich in the grain boundaries of the magnet after annealing,therefore the as-annealed magnet has a higher coercivity than the as-sintered magnet.A distinct Fe-rich layer with the average thickness of 60 nm is found in the grain boundaries in the magnet without Ce-rich alloy addition,but it seems that Fe-rich phase disappears in the magnet with Ce-rich alloy addition.The present work suggests that the further improvement of coercivity in the Ce-Fe-B sintered magnets is expectable by designing the composition and structure of added liquid phase alloys.
基金The support of"Key Laboratory of Special Materials and Preparation in Sichuan Province"
文摘The ribbons of NdFeB/College of Material Science ＆ Engineering, Xihua University, Chengdu 610039, China-Fe composite alloy were prepared by melt spinning and post crystallizing technique. The element distri- butions and phase component of both surfaces of as-spun ribbons were measured by energy dispersive spectrometry （EDS） and X-ray diffraction （XRD）. Because of the centrifugation, a segregation of B, Fe, and Nd concentrations was observed at the cross section. After crystallizing annealing, the element concentration segregation still existed in the as-crystallized ribbons. Due to the segregation of B, Fe, and Nd, the B-rich phase was observed near the wheel side surface. The B-rich phase may deteriorate the magnetic property of NdFeB/a-Fe composite alloy.
