Bowen WANG
,
Weili LIU
,
Guang JIN
,
Jianzhi BI
,
Ximei JIN
,
Zhijun GUO
,
Zhidong ZHANG
材料科学技术（英）
The structure and magnetostriction of R0.5Pr0.5Fex, (R = Dy0.7Tb0.3, 1.10 less than or equal to x less than or equal to 1.85) alloys were investigated. It was found that the matrix of are-melting R0.5Pr0.5Fex, alloys is the (Dy, Tb, Pr) Fe-2 phase with the MgCu2-type cubic structure and the second phase is rare earth-rich phase when x<1.25. In the range of 1.40 less than or equal to x<1.55, the second phase is (Dy, Tb, Pr)Fe-3 and it becomes the main phase when x >1.55. The crystalline structure of mechanically grinding R0.5Pr0.5Fex, alloys is similar to that of the are-melted alloys. The magnetostriction of the alloys increases with increasing Fe content when x less than or equal to 1.25 and decreases when x>1.25.
关键词:
Xinguo ZHAO
,
Zhidong ZHANG
,
Zhijun GUO
,
Wei LIU
,
Dianyu GENG
,
Baozhi CUI
材料科学技术（英）
The alloy with nominal composition Sm-2(Fe0.94Ti0.06)(l7) is prepared by are-melting, hydrogenation and nitrogenation processes. The Sm-2(Fe0.94Ti0.06)(17) alloy has a single phase of Sm-3(Fe, Ti)(29) with the Nd-3(Fe, Ti)(29)-type structure. The corresponding hydride phase with the same phase structure of the parent alloy was formed after a hydrogen decrepitation (HD) process at 300 degrees C. The hydrogenation at 800 degrees C mainly shows a HDDR process. The HD and nitrogenation at 500 degrees C result in increasing the Curie temperature of the alloy by 72 degrees C and by 158 degrees C due to lattice expansions, respectively. The anisotropic and isotropic Sm-3(Fe, Ti)(29)Ny magnets are obtained after HD, HDDR and the consequent nitrogenation, respectively. The optimum magnetic properties of Sm-3(Fe, Ti)(29)Ny powders achieved in the above two processes are: (i) B-r=0.82 T, H-i(c)=4.48 kA/cm, (BH)(max)=54.3 kJ/m(3), (ii) B-r=0.68 T, H-i(c)=8.14 kA/cm, (BH)(max)=66.4 kJ/m(3).
关键词:
Dianyu GENG
,
Zhidong ZHANG
,
Baozhi CUI
,
Zhijun GUO
,
Wei LIU
,
Xinguo ZHAO
材料科学技术（英）
The structure and magnetic properties of SmyFe(100-1.5)yC(0.5y)(y=8 similar to 20) alloys prepared by mechanical alloying (MA) from Sm, Fe and graphite have been investigated systematically. In order to improve hard magnetic properties of the alloys prepared by mechanical alloying, a new method consisting of re-milling and re-annealing was developed. After being re-milled and re-annealed, the Curie temperature T-C of the Sm-Fe-C alloys changes. The T-C of 2:17 phase increases, whereas the T-C of 2:14:1 phase decreases. After being re-annealed at low temperatures, the grain sizes of hard phases are smaller than those in the alloys annealed at high temperatures. The effects of Co or Ti substitution for Fe are studied.
关键词:
Jian ZHANG
,
Xiaokai SUN
,
Wei LIU
,
Baozhi CUI
,
Xinguo ZHAO
,
Zhidong ZHANG
材料科学技术（英）
Structure and magnetic properties of the nanocomposite magnets prepared by mechanical alloying procedure with composition 55 wt pct Nd (Fe0.92B0.08)5.5+45 wt pct a-Fe, 55 wt pct Nd(Fe0.8-xCo0.12Nbx B0.08)5.5+45 wt pct a-Fe (x=0.00, 0.01, 0.03) and 55 wt pct (Nd0.9Dy0.1) (Fe0.77Co0.12Nb0.03B0.08)5.5+45 wt pct a-Fe were studied. It was found that substitution of Co for Fe could significantly improve the permanent magnetic properties of the nanocomposite magnets and typically, the maximum magnetic energy product was increased from 104.8 kJ/m3 (13.1 MGOe) to 141.6 kJ/m3 (17.7 MGOe). In contrast to the case of conventional nominally single-phase magnets, the addition of Nb results in promoting the growth of a-Fe grain and is thus unfavorable for the improvement of permanent magnetic properties of the nanocomposites. Although the addition of Dy can increase the coercivity of the magnets, the increase of magnetic anisotropy of hard phase leads to decrease of the critical grain size of soft phase. Additionally it causes the difficulty of preparing the nanocomposites because it is more difficult to control the grain size of soft phase to meet the requirement of appropriate exchange coupling between hard and soft grains.
关键词:
Dingkang XIONG
,
Xiaokai SUN
,
Liangyue XIONG
,
Wei LIU
,
Tong ZHAO
,
Zhidong ZHANG
材料科学技术（英）
Positron annihilation behaviors have been studied in the single phase Nd2Fe14B magnet and the nanocomposite Nd2Fe14B/alpha -Fe magnet, prepared by melt spinning. The results showed that the number of vacancy-cluster at grain boundaries increases with increasing annealing temperature for the both types of magnets. The increase of this kind of defect can improve the coercivity of the single-phase magnet. Conversely, the increase of vacancy-cluster amount leads to decreasing of the coercivity for the nanocomposite magnet. It implies that the mechanism of dominant magnetic hardening for the two types of magnets is different, and the domain walls pinning mechanism in the single-phase magnet and the reversal magnetization nucleation mechanism in the nanocomposite magnet operate, respectively.
关键词:
Zhijun GUO
,
Zhidong ZHANG
,
Xinguo ZHAO
,
Bowen WANG
,
Dianyu GENG
材料科学技术（英）
Structure and magnetostriction of Dy1-xPrxFe2 (0 less than or equal to x less than or equal to 0.5), Dy0.6Pr0.4(Fe1-yTy)(2) (0 less than or equal to y less than or equal to 0.6), and Tb1-zPrz(Fe0.4Co0.6)(2) (0 less than or equal to z less than or equal to 1.0) alloys (T=Co, Ni) have been investigated. It is found that the matrix of the alloys Dy1-xPrxFe2 is a single phase (Dy, Pr)Fe-2 with MgCu2-type structure and the second phase is (Dy, Pr)Fe-3 when x less than or equal to 0.2. The amount of (Dy, Pr)Fe-3 phase increases with increasing Pr content and becomes the main phase when x=0.4. The matrix of Dy1-xPrxFe2 is found to be the (Dy, Pr)(2)Fe-17 phase with Th2Zn17-type structure when x=0.5. It is found that the amount of the cubic Laves phase (Dy, Pr)(Fe, Co)(2) in the Dy0.6Pr0.4(Fe1-yCoy)(2) increases with increasing Co concentration when 0 less than or equal to y less than or equal to 0.6. The substitution of Ni for Fe is nearly not favorable for the formation of the cubic Laves phase (Dy, Pr)(Fe, Ni)(2) in (Dy1-xPrx)Fe-2. The matrix of (Tb1-zPrz)(Fe0.4Co0.6)(2) is a (Tb, Pr)(Fe, Co)(2) phase with the MgCu2-type cubic Laves structure and a second phase of small amount is (Tb, Pr)(Fe, Co)(3) phase when z less than or equal to 0.2, z=0.5 and 1.0. When 0.2
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