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
TEM examination proves that the second phase particle within the as-forged Ti-55alloy consists of either bright or dark 'matrix' (nano-Nd3Sn) and some small dark blocks (SnO) dispersed in the 'matrix'...TEM examination proves that the second phase particle within the as-forged Ti-55alloy consists of either bright or dark 'matrix' (nano-Nd3Sn) and some small dark blocks (SnO) dispersed in the 'matrix'. The HREM observation shows that the nanoNd3Sn phase is roughly spherical and about 3-15nm in diameter, and the grain boundaries with atout 1nm width are 'gas-like' structure.展开更多
The morphologies of the Nd-rich phase particles in the Ti-5Al-4Sn-2Zn -1Mo-0.25Si-1Nd alloy after high temperature deformation are investigaied by optical microscope and transmission electron microscope. It is found t...The morphologies of the Nd-rich phase particles in the Ti-5Al-4Sn-2Zn -1Mo-0.25Si-1Nd alloy after high temperature deformation are investigaied by optical microscope and transmission electron microscope. It is found that the Nd-rich phase particles are 1.0～14 μm in diameter and uniformly distributed in ihe matrix, and the majority of the particles are elliptical. Under high temperature deformaiton, high stress concentration occurs on the particles, the particles near to sphericity are obtained.展开更多
Nd-rich phase plays an important role in the magnetic properties of sintered NdFeB alloy. The proportion of Nd-rich phase to all the other phases was calculated by using MATLAB 6.5 software. Especially, post-sintered ...Nd-rich phase plays an important role in the magnetic properties of sintered NdFeB alloy. The proportion of Nd-rich phase to all the other phases was calculated by using MATLAB 6.5 software. Especially, post-sintered alloy, post-high-temperature tempered alloy and post-high and low-temperature tempered alloy were analyzed. It was found that the proportion of Nd-rich phase in the three alloys based on SEM (scanning electron microscope) images was about 8.22%, 8.03% and 8.00%, respectively.展开更多
For the as-cast Ti-55 alloy, the morphology of the alloy riser consists of coarse dendrite zone and equiaxial grain zone. The second phase particles are 2.0-25 um in diameter. Some particles appear at grain boundaries...For the as-cast Ti-55 alloy, the morphology of the alloy riser consists of coarse dendrite zone and equiaxial grain zone. The second phase particles are 2.0-25 um in diameter. Some particles appear at grain boundaries, the others precipitate within grains. The shapes of the particles are mainly ellipsoids, and a few kinds of short needle-like and block v morphologies. The Nd-rich phase particles are enriched in the liquid before the inter face and are engulfed along the solidification plane-front. Finally, bands of Nd-rich phase par-ticles form parallel to the advancing solidification plane-front.展开更多
Nd-Fe-B hot-pressed(HP) magnet prepared from melt-spun MQU-F flakes features coarse grains(CG)with the average size of both 200 nm(CGS) and 700 nm(CGL) at flake boundary.The grain growth at the flake boundary of Nd2 F...Nd-Fe-B hot-pressed(HP) magnet prepared from melt-spun MQU-F flakes features coarse grains(CG)with the average size of both 200 nm(CGS) and 700 nm(CGL) at flake boundary.The grain growth at the flake boundary of Nd2 Fe14B/α-Fe composite HP magnet before and after diffusion of low-melting-point Pr82Cu18 phase was investigated,revealing the indispensable role of surface RE-rich phase of meltspun flakes in the formation of CG in HP magnet.The dominant role of surface oxygen content of melt-spun flakes in the formation of CGL has been clarified with etching method.The HP magnet prepared from the etched flakes with dramatically decreased oxygen content exhibits the CG regions merely with homoge neous equiaxed CGS at flake boundary.Consequently,the coercivity(μ0 Hc) shows significant increase while remanent magnetization(μ0 Mr) inappreciable change.Further investigation with sieving method reveals the elimination of CGL via removal of the fine Nd-Fe-B flakes smaller than 54 μm due to their much higher oxygen content,confirming the dominant role of oxygen content in the formation of CGL.The quantitative analysis on the magnetic properties of the above HP magnets reveals the monotonic increase of coercivity(μ0 Hc) and negligible change of remanent magnetization(μ0 Mr) with decreased oxygen contents of Nd-Fe-B flakes.The maximum value of coercivity(μ0 Hc) increases from2.26 to 2.47 T as the oxygen content decreases from 0.1692 wt% to 0.079 wt%.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.
文摘TEM examination proves that the second phase particle within the as-forged Ti-55alloy consists of either bright or dark 'matrix' (nano-Nd3Sn) and some small dark blocks (SnO) dispersed in the 'matrix'. The HREM observation shows that the nanoNd3Sn phase is roughly spherical and about 3-15nm in diameter, and the grain boundaries with atout 1nm width are 'gas-like' structure.
文摘The morphologies of the Nd-rich phase particles in the Ti-5Al-4Sn-2Zn -1Mo-0.25Si-1Nd alloy after high temperature deformation are investigaied by optical microscope and transmission electron microscope. It is found that the Nd-rich phase particles are 1.0～14 μm in diameter and uniformly distributed in ihe matrix, and the majority of the particles are elliptical. Under high temperature deformaiton, high stress concentration occurs on the particles, the particles near to sphericity are obtained.
基金Funded by the Key Project of Sichan Science Department (2012 JY0045, 2011SZZ029)Key Project of Sichan Education Department (10ZA060, 11ZA161)+1 种基金Key Project of Mianyang Municipal Science and Technology Bureau (10Y002-4)Special Project of MianYang Normal University (2011C02)
文摘Nd-rich phase plays an important role in the magnetic properties of sintered NdFeB alloy. The proportion of Nd-rich phase to all the other phases was calculated by using MATLAB 6.5 software. Especially, post-sintered alloy, post-high-temperature tempered alloy and post-high and low-temperature tempered alloy were analyzed. It was found that the proportion of Nd-rich phase in the three alloys based on SEM (scanning electron microscope) images was about 8.22%, 8.03% and 8.00%, respectively.
文摘For the as-cast Ti-55 alloy, the morphology of the alloy riser consists of coarse dendrite zone and equiaxial grain zone. The second phase particles are 2.0-25 um in diameter. Some particles appear at grain boundaries, the others precipitate within grains. The shapes of the particles are mainly ellipsoids, and a few kinds of short needle-like and block v morphologies. The Nd-rich phase particles are enriched in the liquid before the inter face and are engulfed along the solidification plane-front. Finally, bands of Nd-rich phase par-ticles form parallel to the advancing solidification plane-front.
基金Project supported by the Ningbo Science and Technology Major (2017B10002,2019B10093)the National Natural Science Foundation of China (51671207,51301192)Zhejiang Province Technology Application Research (LGG19E010001)。
文摘Nd-Fe-B hot-pressed(HP) magnet prepared from melt-spun MQU-F flakes features coarse grains(CG)with the average size of both 200 nm(CGS) and 700 nm(CGL) at flake boundary.The grain growth at the flake boundary of Nd2 Fe14B/α-Fe composite HP magnet before and after diffusion of low-melting-point Pr82Cu18 phase was investigated,revealing the indispensable role of surface RE-rich phase of meltspun flakes in the formation of CG in HP magnet.The dominant role of surface oxygen content of melt-spun flakes in the formation of CGL has been clarified with etching method.The HP magnet prepared from the etched flakes with dramatically decreased oxygen content exhibits the CG regions merely with homoge neous equiaxed CGS at flake boundary.Consequently,the coercivity(μ0 Hc) shows significant increase while remanent magnetization(μ0 Mr) inappreciable change.Further investigation with sieving method reveals the elimination of CGL via removal of the fine Nd-Fe-B flakes smaller than 54 μm due to their much higher oxygen content,confirming the dominant role of oxygen content in the formation of CGL.The quantitative analysis on the magnetic properties of the above HP magnets reveals the monotonic increase of coercivity(μ0 Hc) and negligible change of remanent magnetization(μ0 Mr) with decreased oxygen contents of Nd-Fe-B flakes.The maximum value of coercivity(μ0 Hc) increases from2.26 to 2.47 T as the oxygen content decreases from 0.1692 wt% to 0.079 wt%.
