The effects of Zr on crystallization kinetics of Pr Fe B amorphous alloys have been investigated by DTA and XRD methods. It was found that for Pr 8Fe 86- x Zr x B 6 ( x =0, 1, 2) amorphous alloys, the final crystalliz...The effects of Zr on crystallization kinetics of Pr Fe B amorphous alloys have been investigated by DTA and XRD methods. It was found that for Pr 8Fe 86- x Zr x B 6 ( x =0, 1, 2) amorphous alloys, the final crystallized mixture is α Fe and Pr 2Fe 14 B, and the metastable Pr 2Fe 23 B 3 phase occurs during crystallization of Pr 8Fe 86 B 6 amorphous alloy, not during crystallization of Pr 8Fe 86- x Zr x B 6( x =1, 2) amorphous alloys. By analyzing the activation energy of crystallization, the formation of an α Fe/Pr 2Fe 14 B composite microstructure with a coarse grain size in annealed Pr 8Fe 86 B 6 alloy, is attributed to a difficult nucleation and an easy growth for both the α Fe and Pr 2Fe 14 B in the alloy. The addition of Zr can be used to change the crystallization behavior of the α Fe phase in Pr Fe B amorphous alloy, which is helpful to reduce the grain size for the α Fe phase.展开更多
With the aid of 3-dimensional topological analysis methodology,relationships among phage regions on the isothermal section of the Nd-Fe-B phase diagram at 1000℃ and those on vertical sections of the Pr-Fe-B phase dia...With the aid of 3-dimensional topological analysis methodology,relationships among phage regions on the isothermal section of the Nd-Fe-B phase diagram at 1000℃ and those on vertical sections of the Pr-Fe-B phase diagram passing through Pr_2 Fe_(14)B point have been re-discussed and modified.展开更多
Characteristics of magnetic hardening in cast-hot pressed magnet Pr_(19)Fe_(74.5)B_5Cu_(1.5)were stu- died.The microstructure features and virgin magnetization curve reveal a nucleation control- led coercivity mechani...Characteristics of magnetic hardening in cast-hot pressed magnet Pr_(19)Fe_(74.5)B_5Cu_(1.5)were stu- died.The microstructure features and virgin magnetization curve reveal a nucleation control- led coercivity mechanism.Regression analysis shows that the intrinsic coercivity varies inversely as the logarithm of the average grain size: _iH_c(MA/m)=1.7312-0.48161nd(μm) which confirms the randomness of nucleation of reversed domains and the statistical nature of coercivity,indicating that the decrease of grain size would reduce the average number of de- fects on its surface and lower the probability of magnetization reversal of a grain and the cu- mulative fraction of the grains that have reversed their magnetization.Coercivity is thus en- hanced.展开更多
The hot deformation process of cast Pr_(19)Fe_(74.5)B_5Cu_(1.5) magnets were studied.It is found that the easy-axes are aligned parallel to the compressive strain direction in vari- ous hot deformation process.During ...The hot deformation process of cast Pr_(19)Fe_(74.5)B_5Cu_(1.5) magnets were studied.It is found that the easy-axes are aligned parallel to the compressive strain direction in vari- ous hot deformation process.During hot deformation,the crushing of Pr_2Fe_(14)B matrix grains and the relative slip and rotation between the grains take place and the Pr-rich melt is squeezed out of the magnet,leading to a fine,dense and well-aligned microstruc- ture in the fully-deformed magnets.Magnetic properties of B_r=990 mT,_iH_c=880 kA/m and(BH)_m=191 kJ/m^3are obtained.The increase of coercivity is attributed to the fine Pr_2Fe_(14)B grains and the thin Pr-rich phase layer continuously distributed at the grain boundaries.The increasing remanence is resulted primarily from the develop- ment of the easy-axis alignment as well as from the densification of the Pr_2Fe_(14)B matrix. The easy-axis alignment is developed by the relative slip and rotation of the crushed Pr_2Fe_(14)B grains.A full and slow hot deformation is necessary for the good easy-axis alighnment and high magnetic properties.展开更多
Amorphous （Nd,Pr）13Fe80Nb1B6 ribbons were crystallized at 670-730°C for 5-25 min to study the effects of isothermal crystallization on their behavior and magnetic properties. XRD results indicate that the isoth...Amorphous （Nd,Pr）13Fe80Nb1B6 ribbons were crystallized at 670-730°C for 5-25 min to study the effects of isothermal crystallization on their behavior and magnetic properties. XRD results indicate that the isothermal incubation time is 12, 5, and less than 5 min at 670, 700, and 730°C, respectively. High coercivities, with the maximum value of iHc = 1616 kA/m at 700°C for 19 min, measured by a physical property measurement system, are obtained in the crystallized ribbons. This is mainly attributed to the addition of Pr and Nb, because Pr2Fe14B has a higher anisotropic field than Nd2Fe14B, and Nb enriched in the grain boundary regions can not only reduce the exchange-coupling effects among hard grains, but also impede grain growth during the crystallization process. In addition, it should also be related to the characteristics of the furnace that the authors designed.展开更多
文摘The effects of Zr on crystallization kinetics of Pr Fe B amorphous alloys have been investigated by DTA and XRD methods. It was found that for Pr 8Fe 86- x Zr x B 6 ( x =0, 1, 2) amorphous alloys, the final crystallized mixture is α Fe and Pr 2Fe 14 B, and the metastable Pr 2Fe 23 B 3 phase occurs during crystallization of Pr 8Fe 86 B 6 amorphous alloy, not during crystallization of Pr 8Fe 86- x Zr x B 6( x =1, 2) amorphous alloys. By analyzing the activation energy of crystallization, the formation of an α Fe/Pr 2Fe 14 B composite microstructure with a coarse grain size in annealed Pr 8Fe 86 B 6 alloy, is attributed to a difficult nucleation and an easy growth for both the α Fe and Pr 2Fe 14 B in the alloy. The addition of Zr can be used to change the crystallization behavior of the α Fe phase in Pr Fe B amorphous alloy, which is helpful to reduce the grain size for the α Fe phase.
文摘With the aid of 3-dimensional topological analysis methodology,relationships among phage regions on the isothermal section of the Nd-Fe-B phase diagram at 1000℃ and those on vertical sections of the Pr-Fe-B phase diagram passing through Pr_2 Fe_(14)B point have been re-discussed and modified.
文摘Characteristics of magnetic hardening in cast-hot pressed magnet Pr_(19)Fe_(74.5)B_5Cu_(1.5)were stu- died.The microstructure features and virgin magnetization curve reveal a nucleation control- led coercivity mechanism.Regression analysis shows that the intrinsic coercivity varies inversely as the logarithm of the average grain size: _iH_c(MA/m)=1.7312-0.48161nd(μm) which confirms the randomness of nucleation of reversed domains and the statistical nature of coercivity,indicating that the decrease of grain size would reduce the average number of de- fects on its surface and lower the probability of magnetization reversal of a grain and the cu- mulative fraction of the grains that have reversed their magnetization.Coercivity is thus en- hanced.
文摘The hot deformation process of cast Pr_(19)Fe_(74.5)B_5Cu_(1.5) magnets were studied.It is found that the easy-axes are aligned parallel to the compressive strain direction in vari- ous hot deformation process.During hot deformation,the crushing of Pr_2Fe_(14)B matrix grains and the relative slip and rotation between the grains take place and the Pr-rich melt is squeezed out of the magnet,leading to a fine,dense and well-aligned microstruc- ture in the fully-deformed magnets.Magnetic properties of B_r=990 mT,_iH_c=880 kA/m and(BH)_m=191 kJ/m^3are obtained.The increase of coercivity is attributed to the fine Pr_2Fe_(14)B grains and the thin Pr-rich phase layer continuously distributed at the grain boundaries.The increasing remanence is resulted primarily from the develop- ment of the easy-axis alignment as well as from the densification of the Pr_2Fe_(14)B matrix. The easy-axis alignment is developed by the relative slip and rotation of the crushed Pr_2Fe_(14)B grains.A full and slow hot deformation is necessary for the good easy-axis alighnment and high magnetic properties.
基金supported by the National Natural Science Foundation of China (No. 50744014)the National Basic Research Foundation (No. 2004CCA04000)+3 种基金Science and Technology Department of Zhejiang Province (Nos. 2008C21046 and 2008C11086-1)the Natural Science Foundation of Zhejiang Province,China (No. Y406389)the Research and Development Program of Ningbo Bureau of Science and Technology (No. 2006B100054)K.C.Wong Magna Found in Ningbo University
文摘Amorphous （Nd,Pr）13Fe80Nb1B6 ribbons were crystallized at 670-730°C for 5-25 min to study the effects of isothermal crystallization on their behavior and magnetic properties. XRD results indicate that the isothermal incubation time is 12, 5, and less than 5 min at 670, 700, and 730°C, respectively. High coercivities, with the maximum value of iHc = 1616 kA/m at 700°C for 19 min, measured by a physical property measurement system, are obtained in the crystallized ribbons. This is mainly attributed to the addition of Pr and Nb, because Pr2Fe14B has a higher anisotropic field than Nd2Fe14B, and Nb enriched in the grain boundary regions can not only reduce the exchange-coupling effects among hard grains, but also impede grain growth during the crystallization process. In addition, it should also be related to the characteristics of the furnace that the authors designed.
